Prenatal Testing:

An Amniocentesis Primer

by Kmom

Copyright 1996-2004 Kmom@Vireday.Com. All rights reserved.

This FAQ last updated: May 2004

DISCLAIMER: The information on this website is not intended and should not be construed as medical advice. Consult your health provider.

SPECIAL NOTE: This FAQ is an introduction to basic information about amniocentesis; what every woman needs to know in order to make the decision about amniocentesis from a truly informed place.  

For more information about how amniocentesis is affected by obesity, see Large Women and Prenatal Testing: Amniocentesis. Kmom strongly recommends that big moms read this FAQ  on general amnio information first and then the other FAQ.  




"The technology of prenatal diagnosis is usually presented to us as a solution, but it brings with it problems of its own...the technology of prenatal diagnosis has changed and continues to change women's experience of pregnancy."  

---Barbara Katz Rothman, The Tentative Pregnancy


All pregnant women in our technology-happy modern society face confusing choices about prenatal testing, its advantages and disadvantages, and its appropriateness for them. Large pregnant women face even more confusion, since prenatal testing can be slightly harder in this population, and the results can be more confusing. However, since they may be at a somewhat increased risk for problems like neural tube defects, they also face greater pressure than others to have these prenatal tests, even though the tests are often difficult to interpret.

This section is an attempt to present an overview of the most basic prenatal tests most pregnant women in the US are pressured to have, including Ultrasounds, the AFP/Triple Screen Test, Gestational Diabetes tests, and under certain conditions, Amniocentesis.  It is further designed to address the special concerns that large women might have in taking these tests---their fears, any special equipment that might be helpful, the controversies over interpretation of results, whether large women have a higher rate of so-called 'false-positives' on certain tests and why, etc.

It's important to remember that discussing prenatal tests can be simple or incredibly complicated, depending on the degree of detail that is needed and the point under discussion. This FAQ is NOT intended to be a full explanation of all the intricacies of taking and interpreting various prenatal tests, but rather a discussion of them as they pertain to large women instead. A brief description of the test, its purpose, and the procedures are given for each, but the majority of the information is about the specifics of large women and the test. If you need more detail about statistics, interpretation of results, rates of 'false-positives', etc., then be sure to research the many websites devoted to prenatal testing online.

It is also important to realize that most women take these tests without fully considering all of the implications of the test.  Most women think of these as a simple blood test, a cursory part of prenatal care.  They don't consider that intimately wrapped up in the question of prenatal testing is the moral dilemma of abortion and the thorny issue of eugenics. Barbara Katz Rothman points out: 

The history of prenatal diagnosis has roots in the eugenics movement...part of its history has been an attempt to control the gates of life: to decide who is, and who is not, fit to make a contribution to the gene pool.

Katz Rothman is by no means arguing against the use of prenatal testing; she actually presents a number of compelling reasons to consider it.  Her writing is a fair and balanced look at the intricacies and difficulties of this issue.  But she has found through extensive interviewing of parents involved in such testing that most of them were simply unprepared to confront the scope of the types of decisions presented by prenatal testing, and that choosing such testing often changed the way a woman experienced pregnancy in subtle ways.

Parents who are considering using prenatal testing need to be sure they really understand the following issues BEFORE the test takes place: 

More on these kinds of questions is available on other websites about prenatal testing, but it vitally important that parents think about these issues BEFORE they decide whether or not to test.

Readers may feel that there is a strong anti-testing bias in this FAQ.  Kmom's own experiences with prenatal testing (detailed below) have largely been negative, and she is certainly strongly concerned that so many women enter into these tests without really considering what they are doing beforehand.  Part of the purpose of this FAQ is to help women understand the scenarios they might face should their screening test come back positive for possible problems.  And because the overall bias of our technological culture is towards doing more and more testing, she feels an extra responsibility to challenge the automatic assumption that more testing is better.  

However, by no means is she condemning testing completely, nor does she criticize those who do choose to test.  Prenatal testing has certain advantages and in some situations can be a great help.  And under certain circumstances, Kmom would choose to use some of it too.  She is simply pointing out that the issue is far more complex than most clinicians would have patients consider, and that parents need to ask themselves the hard questions before they begin the process.

Finally, it's also important to note that none of these tests are mandatory. Although many women are simply told that they will be taking these tests, it is ALWAYS your right to decline any or all of these tests. Just because you are 35 or over, for example, does not mean that you HAVE to have an amnio, and just because you are a large woman does NOT mean that you have to have the AFP test or gestational diabetes test.  Conversely, it is also your right to request certain tests if they are important to you.  

You have the right to accept or decline any test or treatment during pregnancy. It is YOUR body, and YOU have the ultimate choice. Research the issues carefully so that you make an informed choice, and then either request or decline the test, based on your individual needs and values. Don't let any provider try to bully you into (or out of) tests---listen to their counsel, do your own research, and then MAKE YOUR OWN CHOICES.



Amniocentesis is the process of inserting a needle into the uterus to withdraw some amniotic fluid from around baby for testing.  This amniotic fluid can then be used for testing for certain conditions or birth defects in the baby.  

Complications of amniocentesis can include cramping and bleeding, amniotic fluid leakage, and miscarriage/fetal death.  More unusual complications include fetal respiratory problems, birth defects, uterine infection, and rarely, maternal death.  Because of these potential problems, risks and benefits from amniocentesis must be weighed carefully before making a decision about doing one.

In Kmom's personal opinion, it is wise to be very cautious in deciding to do an amniocentesis. However, each person must weigh the benefits and risks of any procedure and decide for themselves what to do.  In certain situations, it can certainly be a useful test to have.

What An Amniocentesis Does

An amniocentesis uses a hollow needle to remove amniotic fluid from around the baby. This fluid is then cultured, the chromosomes mapped ("karyotyping"), and the fluid tested for various diseases and problems.  

The FAQ on amniocentesis at sums up what an amniocentesis is used for:

[Chromosomal mapping] allows the detection of trisomies (extra chromosomes), monosomies (missing chromosomes), and other structural defects in the chromosomes. Most people have 46 chromosomes, in 23 pairs, but some have an extra copy of one chromosome, called a trisomy because there are three of one chromosome pair. This extra chromosome can lead to a variety of abnormalities. The most common trisomy is called Down syndrome, a trisomy of chromosome pair 21, and it leads to mental retardation and various physical problems. Other common trisomies are trisomies 13 and 18 (which generally cause a baby to die shortly after birth) and sex chromosome trisomies.

Examining the chromosomes also allows the sex to be determined, which may be of particular interest to women who are carriers of sex-linked disorders, such as hemophilia or Duchenne muscular dystrophy. 

In addition to examining the fetal cells for chromosome abnormalities, the amniotic fluid can be tested for levels of [AFP], acetylcholinesterase (AChe), and hemoglobin F. It is possible to detect neural tube defects, including anencephaly, spina bifida, and meningomyelocele (though the use of amniocentesis to detect neural tube defects has been mostly superceded by a combination of the AFP test and high resolution detailed ultrasound). 

It is also possible to detect about 70 metabolic disorders. The tests for metabolic disorders, however, are only done if family history warrants, and will not be done for women being referred for amnio due to age or results on the AFP test or Down's screen. If there is no history of genetic disease in the family, a genetic analysis will not be performed, only a chromosomal analysis. Chromosomal analysis is performed at most large hospitals and some private labs. Genetic analysis is only performed in a few labs in the country and is significantly more expensive. 

Amniocentesis to diagnose birth defects is usually done between the 14th and 20th weeks of pregnancy, most commonly at weeks 15-16.  Amnios can also occur in late pregnancy to test the maturity of the baby's lungs if early delivery is being considered for some medical reason.  Occasionally, amniocentesis is used for other reasons as well.

However, most commonly, amniocentesis is done to check for birth defects and other problems in the baby.  Parents must remember that it does not detect ALL birth defects, and a "normal" amniocentesis does not guarantee a "normal" baby.  For chromosomal disorders, it is a very accurate test, but one that is not without potential risks.   

How An Amniocentesis is Done

In an amniocentesis, the mother is generally given genetic counseling first to try and clarify the parents' genetic heritage and any possible genetic risks. It is a good idea to have researched your family history as much as you can ahead of time, before the genetic counseling appointment.  

Mothers having an amniocentesis should be sure to get plenty of fluids in the week or so before the test.  Poor maternal hydration can sometimes decrease the level of amniotic fluid in the uterus, and this in turn could make getting enough fluid for the test difficult.  Good hydration may help increase the level of amniotic fluid and make it easier to get enough.  In addition, the targeted ultrasound just before the amniocentesis may be helped by a bit of extra fluid in the bladder.  Therefore, it is probably a good idea to be well-hydrated before the test, but you don't need to drink excessive amounts.   

After genetic counseling, a "level two" ultrasound is then done to check for any signs of fetal abnormalities, to check the baby's heartbeat, to determine the position of the baby and of the placenta, to examine closely the main fetal structures, and to double check the baby's gestational age.  A "level two" ultrasound does not mean that any special equipment or intensity of ultrasound is used; it simply means that they take more time to do the ultrasound and are looking more directly for certain problems.  This is often referred to as a "targeted" ultrasound.  

Ultrasound is used to determine the best location for placing the needle---a pocket of substantial amniotic fluid well away from the baby and umbilical cord.  When amnios first came into use, they were done "blind" (without continuous ultrasound guidance during the amnio), and this resulted in a number of disastrous outcomes, including occasional cases of horrifying fetal damage and death.  Modern amniocentesis is done with continuous ultrasound and is much less dangerous.

Continuous ultrasound during an amnio allows the doctor to see a constant view of the needle's path and where the baby is located at all times.  If the baby moves near the needle's path at any point, the doctor can then reposition the needle, or if necessary, withdraw the needle and try again in a different location. Continuous ultrasound has eliminated a great deal of the risk formerly associated with amniocentesis, but at times babies still do get "stuck" by amnio needles.  Rarely is it serious, however.

For the amniocentesis, the mother lies flat on her back on a table.  Iodine solution is swabbed onto her belly in order to cleanse the area thoroughly, and sterile drapes are placed around the area.  A local anesthetic may be used to deaden the area where the needle will go in, but is often not used since the pain is usually minimal and a local means administering a second needle insertion.  A thin, hollow needle is then inserted into the abdomen and uterus, using continuous ultrasound to guide the process.  

In mid-second trimester amnios, about 2 tablespoons of amniotic fluid are removed through the needle; in first-trimester amnios (now not usually done), a little less is removed in order to minimize any possible effects on the baby.  The first bit of amniotic fluid is discarded so that the chances of contamination with the mother's blood or cells is minimized, then the rest of the fluid is removed.  This part of the process only takes a few minutes if everything goes well.  

After the fluid sample is taken, the doctor checks the baby's heartbeat to be sure all is normal.  The fluid sample is then sent off to a lab to be analyzed. The mother's body is thought to replace the amniotic fluid within about 12 hours to a few days of the procedure.   After the amniocentesis, most doctors recommend taking it easy for a few hours or a few days.  Most tell the mother to avoid lifting heavy objects and prolonged standing.  

Living cells from the fetus exist in the amniotic fluid, and these cells are grown in a laboratory for one to two weeks.  These are then tested for chromosomal abnormalities and sometimes for various genetic birth defects. Results usually can take one to three weeks to arrive, although they average about two weeks in most cases. 

The levels of alpha fetoprotein in the amniotic fluid are also checked for the possibility of neural tube defects.  Because this can be measured directly from the fluid, without any culturing, results of this test may take only a few days.  This test may be even more accurate than the AFP/triple test that is done from a maternal blood draw but some research suggests that its use has become outdated and unnecessary.

There is a new method of analysis for amniocentesis that reveals results faster, but less completely.  This is called Fluorescent In Situ Hybridization, or FISH.  According to Mark Perloe at

[FISH] involves using special dyes targeted to specific chromosomes.  Each dye glows a different color under fluorescent lighting.  At present, we can only test for four or five different chromosome pairs using this technique.  Normal cells have 23 pairs of chromosomes; an abnormal fetus may have an extra chromosome or may be missing one from a pair. Since we can't test all the chromosome pairs using FISH, this method only picks up a portion of the potential chromosomal anomalies that may occur.  Luckily, the most common problems are picked up using this screening method.  As results from this test can be available within a few hours, FISH is gaining in popularity.  

What An Amniocentesis Feels Like

Many women worry that an amniocentesis will hurt.  Most literature on amniocentesis tells women that it will not hurt at all, or that it will only hurt a tiny bit.  Dr. Marjorie Greenfield at states, "This procedure...hurts only a bit more than getting blood drawn, and less than getting a shot, or having an IV started."

Actually, women's experiences vary quite a bit.  Some women report that the amnio didn't hurt at all, some women report only a feeling of significant pressure (especially when the amniotic fluid is being withdrawn), some women report a feeling of cramping when the needle goes into the uterus, and still other women report that the amniocentesis was quite painful.  

Kmom's Story: My amnio certainly hurt more than "getting a shot or having an IV started."  Putting the needle into the skin felt about like getting a shot, not too bad.  When the needle pierced the uterus, though, it was definitely painful, about like a very strong menstrual cramp---painful, but tolerable.  

However, because the baby moved, they had to withdraw the needle and re-insert it a second time.  This time the procedure was definitely very uncomfortable, probably because I had a contraction during the insertion and it was difficult to get the needle in. In order to get the fluid out, the doctor pushed very very hard on me and I felt great pressure as he tried to withdraw enough fluid for the test.  At that point, it was definitely extremely uncomfortable, even painful, and the atmosphere in the room was very tense. Eventually they got enough fluid for the test and withdrew the needle.  What a relief when it was finally gone! 

My amnio experience did cause me significant discomfort/pain, much more than "getting a shot" or "getting blood drawn."  However, I also know women who have said that the procedure did not hurt at all.  In all likelihood, the experience varies according to the skill of the doctor and the circumstances of the amnio.  The fact that I had a Braxton-Hicks contraction during the amnio probably was a significant part of why my experience was painful.

Most doctors also probably underestimate the amount of discomfort involved in an amnio.  Even so, usually the procedure is not as painful as most women anticipate it will be, and many women report that the experience was only mildly uncomfortable.  However, each woman's experience is different and depends on a number of different variables. 

After an amnio, most women experience at least some degree of cramping.  Most doctors recommend resting until the cramping has subsided, and taking it easier than usual for the next few days.  Avoid heavy lifting during this time, even if you are feeling well and have had no spotting or cramping.  Within a week or so, you should feel back to normal or very close. 

Possible Problems During the Amniocentesis

Most of the time, amniocentesis goes quite smoothly.  But some of the time, amnios can become more difficult, or may encounter significant problems during the procedure.

Several factors may be more predictive of a difficult amnio procedure.  These include uterine fibroids, low amniotic fluid levels, a retroverted uterus, maternal obesity, and past history of vaginal bleeding in the pregnancy (Johnson 1999).  However, many people with these situations have had an amnio without problems, so these factors do not always signify that there will be problems.

Sometimes more than one needle insertion must be used.  If the baby moves near where the needle is going in, the needle may have to be pulled out and reinserted in a different spot.  Or the spot they selected may not be turn out to be very good and they must try again.  

Sometimes the doctor has difficulty getting the needle in, especially if the mother has a Braxton-Hicks contraction before or during the procedure [as happened to Kmom, see above].   Sometimes a problem known as amniotic membrane "tenting" occurs, where the membranes resist penetration by the needle and are pushed back but not penetrated by the needle.  This may be more associated with fetuses with chromosomal abnormalities like Down Syndrome, but also is more common in earlier amniocentesis procedures (Johnson 1999). 

Sometimes a "bloody tap" occurs, where blood is found in the amniotic fluid.  This blood may be from the needle insertion in the mother, it may occur because the placenta was encountered, or it may come from the fetus.  Blood-stained amniotic fluid is generally associated with more complicated and problematic amnios, but by itself is not a cause for immediate alarm.  In other words, problem amnios have bloody taps associated with them more often, but a bloody tap alone does not necessarily mean there will be problems.  

Every needle insertion raises the risk for problems so it is best to avoid multiple insertions whenever possible.  Most doctors will only do two needle insertions in one amnio session; if they cannot get good results in two insertions, they will often tell mothers to come back and try again in a week or so.  If the first needle insertion goes badly, mothers may want to consider whether to continue the amnio at all. Certainly if success does not come after two needle insertions, the amnio should probably be abandoned that day and, if desired, tried again later.

Sometimes the doctor seems to complete the amnio just fine but later finds out he did not get enough fluid, or the fluid is contaminated by blood or maternal cells.  In this case, the mother will be called to come back for a repeat amniocentesis.  Another possible problem occurs when lab workers are unable to culture enough cells from the amniotic fluid to do karyotyping.  This would also  necessitate a second amnio. 

Needing a repeat amnio because of culture failure is thought to occur about 2%-6% of the time in second trimester amnios, and up to 18% of the time in first-trimester amnios.  Sometimes culture failure is more common with certain fetal abnormalities, but most of the time the baby is normal and the lab just needs more amniotic fluid with fresh fetal cells.

Repeat amniocentesis happens more often than people think. Barbara Katz Rothman, author of The Tentative Pregnancy: How Amniocentesis Changes the Experience of Motherhood, found that 10% of the women having amnios that she interviewed ended up having more than one amniocentesis. The medical literature reflects smaller numbers (especially for second trimester amnios), but even so, the numbers are still significant.  The possibility for needing a repeat amnio is one of the risks of amnios that women are rarely adequately informed about.

Again, remember that at any point, you can decide not to continue with amniocentesis. If problems are encountered during the amnio or a repeat amnio is needed, some women choose to just stop the process altogether, or to stop it and wait a while before trying again.  The decision is ALWAYS up to you----it is your body and your baby.  You have the ultimate power to decide whether or not to continue. 

Possible Problems After the Amniocentesis

According to the March of Dimes, about 1-2% of women experience cramping, spotting/bleeding, or leakage of amniotic fluid after an amniocentesis.  Anecdotally, the rates seem higher when talking to women who have been through amnios.  

Most women report some feelings of cramping after an amnio, though the cramps are usually mild. Spotting is more unusual but does still happen to some women.  Leakage of amniotic fluid seems more rare, anecdotally, but it may not be easy to spot this if you are already bleeding.  

Be sure to call your doctor if you have any concerns.  According to various amniocentesis resources, you should contact your healthcare provider if you experience any of the following after an amniocentesis:

It is better to err on the side of caution.  If you experience any problems after an amniocentesis, call your doctors right away and keep them informed.  They can track your symptoms and advise you what to do.  Don't worry about "bothering" them or think that your symptoms are too trivial to mention.  Doctors need to stay fully informed of your condition so they can assess how you are doing and what to do about any problems.

If you are feeling very ill or have symptoms of an infection, don't hesitate to go to the Emergency Room immediately and get checked.  Be sure to let them know you had an amniocentesis.  If you show any signs of infection, you or your partner may need to get assertive in order to get them to take the possibility of infection seriously.  Although medical personnel may discount the possibility because it is rare, infection is a major risk of amniocentesis, and one that can kill (and has).  Be assertive about getting treatment if you suspect you may have an infection. 

Although miscarriage after an amnio is thought to be most common shortly after the procedure, some research indicates that it can still happen even 6-7 weeks after the procedure.  If you do experience problems, even weeks after an amnio, be sure to mention to your health care providers that you recently had an amniocentesis done.  


The Different Types of Amniocentesis Available

Amniocentesis is most commonly done in the middle of the second trimester at about 15-18 weeks, most commonly at about week 15-16.  However, the 2 week delay in getting the results means that if there is a problem and the couple decides to terminate the pregnancy, a late abortion must be done.  The later the abortion, the harder the procedure is physically, and the closer to viability the fetus is (which is harder on the parents emotionally as well).  

Because of this, researchers have experimented with other types of prenatal testing that can be done in the first trimester.  An abortion at that stage is physically easier, and most researchers assume that it is emotionally easier as well (this is debatable).  So there has been a great deal of interest in amniocentesis at earlier stages of pregnancy, as well as another type of prenatal testing called Chorionic Villus Sampling (CVS).  

However, at this time, mid-second trimester amniocentesis remains the diagnostic procedure of choice for most clinicians.  It is associated with less risk for miscarriage and less risk for complications than first-trimester procedures.  If the mother feels it is very important to have a first-trimester procedure done, current research supports choosing Chorionic Villus Sampling over Early Amniocentesis.  

Mid-Trimester Amniocentesis (Second Trimester)

Mid-trimester amniocentesis is done in the second trimester, usually between 15-18 weeks.  Although some resources consider amnios at 14 weeks to be second trimester procedures, research shows that they are probably still associated with increased risks like first-trimester amnios.  Therefore, many resources recommend that amniocentesis not be performed until at least 15 gestational weeks.  

Because amnios are done with the presumption that abortion will be chosen if a birth defect is found, they are usually not done after about 19-20 weeks.  This is because after the turn-around time for culturing and testing cells (about 2-3 weeks), the fetus is close to viability (the ability to survive outside the womb, which now occurs at about 24-25 weeks). Thus the optimal time for doing an amniocentesis is considered to be 15-16 weeks, with up to 18 weeks considered acceptable. 

Second trimester amniocentesis has been studied fairly extensively, and long-term follow-up studies have shown that, as a group, children exposed to second-trimester amniocentesis are not substantially more at risk for more long-term complications than children not exposed to amniocentesis.  Amnios still have risks, of course, but the risks seem to be shorter-term risks than longer-term. 

Early Amniocentesis (First Trimester)

Early amniocentesis is done in the first trimester, between 11-14 weeks.  Some resources consider 14 weeks to be part of the first trimester and thus technically an Early Amniocentesis, while others consider it to be part of the second trimester and a traditional amniocentesis.  

Early amniocentesis was studied in a large randomized controlled trial in Canada (CEMAT group, Lancet, 1998).  It was found to be associated with THREE times the rate of miscarriage compared to later amniocentesis.  This same study found a striking ten-fold increased risk of club foot (talipes) with early amniocentesis as well.  

Early amniocentesis is probably also associated with fetal respiratory problems.  The theory is that because there is a smaller amount of amniotic fluid present this early in pregnancy, a removal of even a small amount can negatively impact the fetus' lung development more strongly than later in pregnancy.   Some research has shown that early amniocentesis that takes less amniotic fluid has less of a negative impact of fetal respiratory status, but even so, the rates of respiratory problems are still far greater than those encountered with second-trimester amniocentesis.

Because of the increased rate of miscarriage, clubfoot, and respiratory problems, Early Amniocentesis has largely been discredited for prenatal testing at this time. 

Early Amniocentesis Versus Chorionic Villus Sampling (CVS)

Until recently, one of the burning debates in prenatal diagnosis circles was whether Chorionic Villus Sampling or Early Amniocentesis was the better choice for prenatal diagnosis in the first trimester.  

Chorionic Villus Sampling can be done earlier in pregnancy than mid-trimester amniocentesis or early amniocentesis.  Although it has been done earlier, CVS is usually done at about 10-12 weeks of pregnancy in order to minimize the risk of limb deformities that were found in studies of CVS done at <10 weeks.  

Early Amniocentesis is usually done between 11-13 weeks, and of course Midtrimester Amniocentesis is usually done at about 15-16 weeks gestation.  So CVS does offer a slight time advantage over the two amniocentesis procedures.

The disadvantage of CVS is that it carries a higher risk of miscarriage than second trimester amniocentesis.  It also carries a higher rate of culture failure than amniocentesis, meaning that more repeat CVS tests must be done.  In addition, CVS cannot test for neural tube defects, so if detecting this is important to women, either the AFP/triple test or a second-trimester amniocentesis must also be done, even after the CVS test is completed.  Furthermore, CVS may miss abnormal chromosome karyotypes in about 1% of cases, resulting in a 'false negative' diagnosis. 

Another disadvantage of CVS is that sometimes a reported chromosomal abnormality is restricted to the chorionic villi only and is not actually found in the baby.  CVS samples chorionic villi and predicts fetal defects based on this placental material, but some chromosomal mosaicism is confined to the placenta only. Thus the possibility exists that a baby may be diagnosed with birth defects and aborted when actually the abnormality is found only in the placenta.   

The biggest advantage of CVS is that it is done earlier in pregnancy, when terminating a pregnancy is easier physically and perhaps mentally.  Dr. Marjorie Greenfield of reports that CVS "is particularly useful in cases where there is a high likelihood of finding a genetic problem, such as in couples who both carry a serious recessive genetic trait, giving their baby a 25% chance of being affected."

Despite the potential problems of CVS, the risk for fetal loss, clubfoot, and other problems is greater in the Early Amniocentesis group.  At this time, if a first-trimester procedure is desired, CVS is the procedure of choice.  

However, if the choice is between first trimester CVS, first trimester Early Amniocentesis, and Second Trimester Amniocentesis, the risks are clearly lowest with Second Trimester Amniocentesis.  Authorities agree that between these three choices, Second Trimester Amniocentesis is the invasive prenatal test of choice (Jauniaux 2000, Alfirevic 2000).  

If you are at high risk for a chromosomal or genetic disorder and/or you are sure you would choose abortion if a birth defect is found, then CVS may be the best prenatal test for you because the abortion could be done earlier, when it is less dangerous to the mother, and before the pregnancy is obvious to others. Otherwise, the prenatal test of choice is probably Second Trimester Amniocentesis.  

And of course, many women choose no prenatal testing at all, or limit their prenatal testing to ultrasounds.  Prenatal testing is never mandatory.


Reasons for Doing Amnios

There are many reasons for doing amniocentesis, but the most common reason is to check for fetal birth defects. Other reasons can include checking fetal lung maturity near term, and occasionally in late pregnancy to assess anemia in babies with Rh disease.  Occasionally, amnios are used to treat polyhydramnios (excess amniotic fluid), or to check for uterine infections.

Checking For Birth Defects

A baby's chromosomes can be examined through amniocentesis for chromosomal birth defects.  This process is described as following at

The cells in the fluid are largely from the amniotic membrane (called "amniocytes") and some fetal skin cells.  Since they are not actively growing, they need to be cultured and stimulated to grow which takes about 7-14 days.  After that, the cells are "harvested" and treated to make the chromosomes visible in their expanded form.  The cells are then broken to release the chromosomes which are stained with various techniques for visualization of the "bands" on each chromosome and to allow identification.  The chromosomes are counted and matched up in 23 pairs, and then examined for evidence of missing pieces or extra pieces.

What are the most common birth defects that an amnio can detect? Virtually all chromosomal defects can be detected with amniocentesis.  Many (but not all) genetic disorders can also be detected using amniocentesis.  In addition, some types of developmental fetal malformations (such as neural tube defects or abdominal wall defects) can be detected through analyzing amniotic fluid, as can certain biochemical disorders.

Down syndrome is the most common chromosomal problem people use amniocentesis to detect.  In Down syndrome (trisomy 21), there is a combination of physical and mental abnormalities caused by the presence of an extra 21st chromosome.  According to the March of Dimes, "Down syndrome occurs in approximately one in 1250 children born to women in their 20s.  The chances increase to one in 400 by age 35, and one in 100 at age 40."  Other syndromes amniocentesis can check for include trisomy 13, 18, etc., plus Turner and Cri du Chat syndromes.

Although taking the test is certainly not mandatory by any means, amnios are most commonly offered to the following groups:

The most common reason an amnio is done is maternal age of 35 or over. However, amniocentesis is by no means required in this group, and in fact although the risk for birth defects increases as a woman ages, a woman is still much more likely to have a 'normal' baby even well into her 40s.  

Some research suggests that women with high AFP results may be at increased risk for miscarriage if an amniocentesis is performed to look for Neural Tube Defects.  The Clinical Guidelines of the Royal College of Obstetricians and Gynecologists suggests that "Detailed ultrasound, rather than amniocentesis, should be offered first for the diagnosis of neural tube defect wherever possible." 

Of course, if you are younger than 35 but greatly concerned about the possibility of birth defects (even without the presence of family history or prior birth defect), you can always request to have an amnio.  Nearly all doctors and prenatal diagnosis centers will consent to an amnio in a woman younger than 35 if she requests one to detect birth defects.  Insurance doesn't always cover the cost, but increasingly, more insurance companies are agreeing to pay for amniocentesis even in women at low risk for birth defects if they request testing.

Checking Fetal Lung Maturity

Checking for birth defects is not the only reason amnios are done. Sometimes an amnio is done near the end of pregnancy to see if the baby's lungs are ready for baby to start breathing on its own after delivery. If your health provider is considering an early delivery for you because of pre-eclampsia, gestational diabetes, or other medical considerations, an amnio may be recommended to determine lung readiness before early induction or an elective cesarean.

An amnio to check for fetal lung maturity is generally a fairly easy procedure.  It does not carry the risk that Early Amniocentesis and Second Trimester Amniocentesis carries.  Because the uterus is bigger and closer to the surface, it is technically much easier to perform and reportedly more comfortable for the mother as well.  

When checking for fetal lung maturity near term, the amounts of phosphatidyl glycerol (PG) is checked as well the Lecithin/Sphingomyelin ratio (L/S ratio).   Although some doctors only order L/S ratios, fetal lung maturity is measured more accurately if PG levels are included as well.   Be sure to request BOTH be measured if you have an amnio for fetal lung maturity.

Keep in mind that like all tests, sometimes amnios have "false positive" results (tests indicate there might be a problem when there isn't).  In particular, blood or meconium in the amniotic fluid can produce a false L/S ratio.  If you are having an amnio to check fetal lung maturity, ask the doctor to be sure that no blood or meconium seems to be in the fluid.  

One common question is whether fetal lung maturity amnios are necessary after 37 weeks.  It is standard practice to order an amnio to check lung maturity if delivery is contemplated before 37-38 weeks, and generally regarded as unnecessary after 39 weeks.  However, in between is a gray area of 37-38 weeks.  Research and medical standards suggest that an amnio for fetal lung maturity should be done if elective delivery (especially by cesarean) is done before 39 weeks.  

Currently, most doctors will schedule an amnio to check fetal lung maturity if delivery is contemplated at 37 weeks, and this is an important step in preventing respiratory problems in this group.  However, research shows that sometimes an amnio to confirm fetal lung maturity is skipped even at 37 weeks.  This clearly leads to a significant number of preventable cases of Respiratory Distress Syndrome, which can be very serious.

At 38 weeks, many doctors do not "bother" with an amnio to check lung maturity, considering it unnecessary at that point.  Yet research is clear that a number of cases of respiratory problems do occur then and could be avoided if doctors were more careful to check lung maturity well into week 38. 

This is especially important for babies born by elective cesarean.  These babies are at much greater risk for significant respiratory distress because they do not have the benefit of labor to help them prepare for breathing outside the womb.  A relatively high rate of babies born by elective cesarean experience some degree of respiratory problems, and the rate is particularly high in babies taken at 37 and 38 weeks.  At times, these respiratory problems can be very serious.

Research clearly shows that Respiratory Distress Syndrome rarely occurs after 39 weeks but is common at 37 weeks and somewhat common at 38 weeks.  Therefore, most official OB guidelines strongly suggest that elective cesareans be delayed until 39 weeks OR until fetal lung maturity has been established by amniocentesis first.  Kmom strongly agrees.  

Of the two choices, the better option is to wait until 39 weeks if possible.  Babies born by elective cesareans at 39 or 40 weeks do MUCH better in many ways than if born earlier. Waiting an extra week or so can make a LOT of difference in blood sugar stability, jaundice, ability to breastfeed, and readiness to breathe easily.  Although the medical trend currently is to do an elective cesarean at 38 weeks, Kmom strongly believes that waiting until 39 weeks is a better option in the majority of cases, and waiting until 40 weeks is even better.

If medical circumstances dictate that you must deliver earlier than 39 weeks, consider an amniocentesis first to be sure the baby's lungs are ready.  Although most babies born at 37-38 weeks do okay, research clearly supports that many serious cases of respiratory distress at that age can be prevented by documenting lung maturity with an amnio. 

If your doctor recommends early delivery by induction or elective cesarean, be sure to question closely the necessity of such a decision. Early delivery can be lifesaving and very appropriate in many cases, but some elective early deliveries are definitely questionable.  Get a second opinion whenever possible. Don't forget also that fetal dating is not always accurate, and babies thought to be 38 weeks may well be younger.  If in doubt about a baby's age because of longer menstrual cycles or questionable ultrasound dating, be sure to check for fetal lung maturity before delivery. 

In other words, if you feel confident that early delivery is necessary, proceed-----but strongly consider an amnio to check the baby's lung maturity if the baby is not yet 39 weeks or if you are unsure of the baby's true gestational age. 

Rh Disease Monitoring

Amnios can be used to assess the severity of fetal anemia if a baby has developed Rh disease.  Rh negative mothers who have had an Rh positive baby in the past can sometimes develop antibodies in the blood. These antibodies may then attack the red blood cells of a subsequent Rh positive baby (hemolysis), harming it or even killing it.  In addition, there are other, more rare antibodies (Kell, Kidd, Duffy and others) than can develop as well; these act similarly to Rh disease and may cause hemolysis. 

Nowadays Rh disease can usually be prevented by the use of immunoglobins (i.e. Rhogam), but in the past sensitization was more common.  In some cases, if the mother had developed antibodies, the baby of a new pregnancy could be affected severely.  Amniocentesis and cordocentesis (testing the baby's blood from the umbilical cord) could be used to detect the level of anemia in the baby near term, and help the doctor decide whether to deliver early and whether the baby might need a blood transfusion and/or early delivery to save its life.  

Some resources report that if blood type incompatibilities or sensitizations are suspected, amniocentesis is usually done between 18 and 22 weeks to monitor the severity of the problem and to check on the baby's health.  After that, repeated amnios may be needed to see how much an affected fetus has been impacted by sensitization, and to evaluate whether a blood transfusion or early delivery is needed. 

However, amniocentesis is not absolutely required simply because a mother tests positive for antibodies.  Not all patients who test positive for antibodies for Rh or other factors develop hemolytic disease; many of these babies are born without problems at term.  As a result, some doctors are willing to do serial antibody titers (to see if the antibody levels is increasing, indicating the baby may be being compromised) and/or serial ultrasounds (to check on baby's health status) instead of automatic multiple amnios.  An amnio would only then be used should the antibody titer and/or ultrasound indicate the development of a problem.  

Rh disease is so preventable nowadays (and other antibody sensitizations are so rare) that it is unusual for amniocentesis to be used for Rh/Hemolytic Disease monitoring today.  If the mother tests positive for Rh or other antibodies, other less invasive tests can be used before resorting to serial amniocentesis. However, should hemolytic disease begin to occur because of antibody issues, amniocentesis can be a valuable tool in monitoring the progress and health of the baby.

Other Possible Reasons for Doing Amniocentesis

Amniocentesis can be used for other reasons beyond detecting birth defects, checking fetal lung maturity, and monitoring Rh Disease. However, these uses are not common these days, and the chances of any one mother needing an amnio for these problems is quite small.  

The March of Dimes reports that amniocentesis can be used to diagnose massive uterine infections.  If the mother's bag of waters has ruptured prematurely, sometimes an amnio is done to check for such infections.  

Another use of amniocentesis in the past was in pregnancies with too much amniotic fluid (Polyhydramnios).  If the levels of amniotic fluid were really excessive, an amnio could be used to draw off some of the extra fluid as needed.  

However, although sometimes there are other uses, most of the time amniocentesis is used for detecting birth defects etc. in the baby, and occasionally for testing fetal lung maturity near the end of pregnancy if early delivery is being contemplated.  


Risks of Amniocentesis

Amniocentesis is not without risks.  Bleeding and cramping, miscarriage, amniotic fluid leakage, fetal respiratory problems, increased admissions to the Neonatal Intensive Care Unit, uterine infection, clubfoot, etc. are all listed in various resources as potential risks of amniocentesis. 

Cramping is very common after amniocentesis, although it is usually quite mild in most cases.  A smaller percentage of women experience more significant cramping.  Bleeding occurs 2-3% of the time and is usually resolves without problems, but is associated with a somewhat higher rate of fetal loss.  

The risk for miscarriage increases after an amniocentesis, although how much depends on which resource you read.  It is generally thought to increase between 0.5% and 1.0%, depending on the skill of the provider and various other maternal risk factors.  

Amniotic fluid leakage is not uncommon after an amniocentesis. Although most of the time the uterus "seals" itself and replenishes any lost fluid, sometimes fluid loss is of concern and may be connected to increased rates of respiratory problems later on.  

Some research has found an increased risk for long-term respiratory difficulties in the baby after amniocentesis, and perhaps increased admissions to Neonatal Intensive Care Units due to prematurity or breathing problems.  

Uterine infection is also a possible risk.  Although rare nowadays, it does occasionally result in the loss of a baby or mother, as happened recently in England (see below).  

Early amniocentesis has been reported to result in higher rates of birth defects such as Clubfoot (Talipes Equinovarus).  Because early amnios have also been associated with a higher rate of fetal loss, they have largely been discredited as a viable prenatal testing technique at this time.

Some resources state that amniocentesis is more risky in women who have had previous abdominal surgery, previous infection in pelvic organs, or in women who are obese, although they provide no references to back up that assertion.  

However, potential risks of amniocentesis must be kept in perspective.  Several studies have compared babies who underwent second-trimester amniocentesis with babies who were not exposed to second-trimester amniocentesis, and by and large, these studies have not found any differences between groups (see Finegan 1985, 1990, 1996).  One limit of these studies is their small size; they may not be large enough to detect rarer problems.  However, larger studies have detected no differences between groups either (Baird, 1994), with the exception of ABO isoimmunization.  

So while amniocentesis does have some increased risks (most notably miscarriage), for the most part second-trimester amniocentesis is not a highly risky procedure. Early Amniocentesis, on the other hand, has been shown to be much more risky and should be avoided.

Bleeding and Cramping

Most women experience some degree of cramping after an amniocentesis, usually mild and of no long-term significance.  However, any cramping should be reported to your doctor, especially if the cramping is accompanied by any bleeding or amniotic fluid loss.  

Some resources report that 2-3% of women who have had amniocentesis will experience some degree of vaginal bleeding afterwards. This is thought to be "self-limiting" in most cases but because it can be associated with miscarriage after amnios, it should always be reported to the doctor.   

Bleeding may not always occur right away. Sometimes it shows up after several days have passed.  Sometimes, women are feeling fine and begin to resume their lives too early or do some heavy lifting, and then she experiences bleeding (as happened to Kmom).  This is why it is important to take it easy for a while after an amnio, and especially to avoid heavy lifting for a few days afterwards.  

Miscarriage Risk

Does amniocentesis increase the risk for miscarriage?  Although some sources dispute this, most sources state that there is a small increase in the risk of fetal loss after an amnio.  However, miscarriages often occur in pregnancy, even at 16 weeks or more.  How can we determine what losses would occur anyhow and what losses may be directly related to amniocentesis?  This is a difficult question to answer. 

Because some miscarriages would occur anyhow, regardless of whether or not an amnio is done, amnio resources refer to the "excess" risk for miscarriage/fetal loss associated with amniocentesis---that is, the amount that miscarriage rates after amnios are raised above normal background miscarriage levels in women not having amnios.  

The estimates for "excess" risk for miscarriage due to amniocentesis vary greatly.  Some authorities insist there is no increased risk for miscarriage, while others assert the risk is much higher than generally acknowledged.  Probably one reason for the confusion is that studies often have different time protocols.  Some only consider amnio to be relevant if a miscarriage occurs within a few days of the amnio, some within 2 weeks of the amnio, while some contend that miscarriage can occur up to 6-7 weeks after an amnio and still be related to the amnio.  Thus, "excess" miscarriage risk varies from study to study.

Most resources state that the risk for miscarriage increases somewhere between 0.5% to 1% after a second-trimester amnio.  If the risk is 0.5%, that means about 1 in 200 pregnancies miscarries due to amniocentesis (that would not have miscarried otherwise).  If the risk is 1.0%, that means the risk is 1 in 100.   On the other hand, of course, it also means that 99.0 - 99.5% of pregnancies do not miscarry after amniocentesis.  With first-trimester amniocentesis, the "excess" risk for miscarriage is even higher, generally thought to be between 2-5%.

Why would a pregnancy miscarry after amniocentesis?  According to

The cause of the miscarriage may be an infection developing in the uterus, or the waters breaking and starting the uterus to contract, or excessive bleeding. Sometimes the cause is unknown, and sometimes the baby that is miscarried is found to have a genetic disorder, and it is felt the miscarriage may have happened anyway.

Many factors are thought to influence the risk for miscarriage after amniocentesis.  For example, the miscarriage rate depends greatly on the skill of the provider.  Generally speaking, the more skilled and experienced the doctor, the lower the miscarriage rate.  Inexperienced doctors tend to have the highest rates of miscarriage.  

If you do choose to have an amnio, therefore, schedule your  amnio at a center that specializes in amnios, and with a doctor that has done a lot of them in the past, and that does a lot of them on a regular basis each year.  Be sure to ask that doctor the rate of loss in that institution, his own personal rate of loss, how experienced he is, and how many amnios he does per year.

If you are plus-sized, you may also want to request a doctor who has had a lot of experience in doing amnios in women of size, since amniocentesis may be more risky and difficult technically in obese women.  Look for one who is size-friendly and will not berate you for your size, but will be upfront with you about possible risks and concerns.

There are other factors that tend to predispose to fetal loss besides doctor inexperience and skill.  These vary from study to study but may include:

Unfortunately, many women report that none of these factors were discussed with them when making the decision about amniocentesis.  For example, Kmom had a history of prior bleeding in her first pregnancy before her amniocentesis, but was NOT told that this might increase the risk of miscarriage.  Nor was she told that the difficult procedure that she endured and the multiple needle insertions might increase her risk for fetal loss either.  Only later, when the bleeding and cramping subsided and her karyotyping came back "normal," did her genetic counselor share that he had been really concerned about fetal loss for her.  

Fetal loss after amniocentesis is a subject many doctors like to avoid, or dismiss with a short speech on the potential risks.  When it occurs, avoidance of acknowledging your loss may be strong.  Many women have found that the culture of denial is very strong in the medical community, especially when obstetrical intervention results in damage or death to the baby.  Barbara Katz Rothman relates the story of a woman OB who experienced a miscarriage after an amniocentesis and the emotional roadblocks she received from other doctors afterwards.  She was devastated and angered by the lack of support she encountered and the downright denial of any problem by her fellow doctors. 

If you experience a miscarriage after an amniocentesis, be sure to get special counseling and support from people who will understand and listen non-judgmentally to your situation.  Keep in mind that this support may not be from the medical community.  

Amniotic Fluid Leakage

Some sources list the rate of amniotic fluid leakage after amniocentesis as approximately 1-2%.  Most of the time, the fluid loss is fairly minimal.  Because the body is constantly making and replacing amniotic fluid, lost fluid is thought to be replaced within twelve hours to a few days of the procedure.  

Amniotic fluid leakage is more common among women having earlier amnios.  Some research suggests it may also be more common in women who had prior vaginal bleeding in the pregnancy, in women who have already had a number of babies, and in heavier women.   

Amniotic fluid leakage can be an early sign that the baby is going to miscarry.  Most women who experience amniotic fluid leakage do NOT end up miscarrying, but it is a potential sign of it.  Be sure to notify your healthcare provider if you experience any leakage after an amnio, and take it as easy as possible in the meantime.  In all likelihood, the leak will seal over and all will be well, but it is better to be careful in the meantime.

If amniotic fluid leakage continues over time without a miscarriage, there is more concern for prematurity, low birth weight babies, orthopedic problems, and respiratory compromise.  Babies need their amniotic fluid.  If you have continuing fluid leakage, be sure to discuss the issue carefully with your doctor.

Uterine Infection

Because people carry many germs, there is a small but real risk that the amnio needle could become contaminated with germs from the mother's skin, from the skin or gloves of the doctor doing the amnio, or from germs inside the mother's body.  These germs could then be transmitted down into the mother's uterus, where they could infect the amniotic fluid and the baby.  

The March of Dimes reports that the risk for uterine infection after amniocentesis is very small, on the order of less than 1 in 1000.  However, uterine infection can also cause miscarriage and even deadly sepsis in the mother, so while the risk of infection is small, it is potentially very serious.  

A recent British news report confirms this rare but serious risk.  A British woman underwent an amniocentesis in May 2000.  Her uterus was infected with deadly E. Coli bacteria during the amniocentesis, she went into septic shock, began miscarrying her baby, and died of a heart attack caused by septic shock from the amnio.  Both the mother and the baby were lost. 

A gynecological expert speculated that it was likely that the amnio needle had accidentally perforated her bowel during the procedure and that this was the source of the E. Coli bacteria that infected her, although he could not be sure.  The amnio doctor reported he had tried to do the amnio twice, but that there was an "unusually small" amount of amniotic fluid and one of the fluid samples was blood-stained.  

At that point he stopped the amnio and told the woman to return in 5 days for a check-up.  She returned to the hospital within 3 hours with cramps/labor pains, but they did no blood tests on her and sent her away with acetaminophen.   Within a day she was readmitted with vomiting and septic shock.  She suffered a heart attack the next day, and died within minutes of the beginning of surgery.  The coroner confirmed her heart attack and death were direct results of septic shock from the amnio.

It's important to understand that, while horrifying, this story represents a very rare risk of amniocentesis.  The British news report emphasized that this mother was only the second person to die after contracting an E. Coli infection this way.  The story may also illustrate that amniocentesis is more risky when the procedure is difficult, requires more than one try, or when a sample comes back blood-stained.  Or it may simply be one of those rare risks that cannot be avoided completely.

In order to lower the risk for uterine infection, the mother's belly should be swabbed with iodine solution thoroughly before the procedure.  Medical personnel are also supposed to wash their hands thoroughly and glove up before the procedure as well.  If the amnio seems especially difficult or requires more than one try, you might want to reconsider whether to continue with the amnio at that time.  

Although the risk for infection with an amnio is quite small, be sure every precaution is taken if you do decide to have an amniocentesis. Also, if you experience any signs of infection after an amnio (chills, fever, vomiting, headache, muscle aches, dizziness, or a general ill feeling), be sure to see a doctor right away and be sure they take the possibility of infection very seriously. 

Respiratory Difficulties

Several studies have found an increased rate of respiratory difficulties in babies exposed to amniocentesis.  This effect seems particularly strong in Early Amniocentesis, but also is seen in second trimester amniocentesis. Researchers theorize that removal of extra amniotic fluid may somehow impair lung growth during a critical time period of development.

The research about Early Amniocentesis is quite clear that respiratory functions can be affected.  Yuksel (1997) found that:

Procedures performed in the first trimester were independently associated with a high airways resistance.  These results suggest that invasive procedures performed in the first trimester of pregnancy have an adverse effect on perinatal lung function.

Thompson (1992) found that both CVS and EA "may impair antenatal lung growth."  Greenough (1997) also found that "First trimester procedures are associated with increased respiratory morbidity in very young children."

Although most amnio resources attribute respiratory difficulties primarily to first-trimester amnios, there is some evidence that second-trimester amnios may also be associated with respiratory problems.  For example, the website at states:

Babies who have an amniocentesis have about a 1% increase in risk of developing breathing problems at birth, called 'respiratory distress'. Amniotic fluid plays an important part in the development of a baby's lungs. Respiratory distress can be treated, but requires the baby to be cared for in the intensive care nursery for several days.

Annapoorna  (1996) found that children exposed to second trimester amniocentesis had an increased incidence of respiratory illness (57%) compared with controls (30%).  This was an unexpected finding, and they called for further study on the issue.  

Milner (1992) studied 39 full-term babies who had been exposed to second-trimester amniocentesis and also found more lung problems.  They concluded, "This provides further evidence that mid-trimester amniocentesis does have an adverse effect on lung growth and development."  Enkin et al. also cited studies that showed some risk for respiratory problems after mid-trimester amnios (see below).  On the other hand, not all studies have found evidence of increased respiratory difficulties after second trimester amniocentesis (Hunter 1987).  

So while it is clear that first-trimester amniocentesis probably DOES affect lung function, the influence of second trimester amnios is less clear.  Probably it is also a risk factor for respiratory problems, especially with significant or extended amniotic fluid leakage. However, the majority of babies who are exposed to an amniocentesis in the second trimester will not develop respiratory problems.

Ear Problems

Finegan (1990) did find a higher rate of ear problems (especially ear infections) in children who had been exposed to amniocentesis as babies.  If amniotic fluid plays a role in inner ear and mid-ear development, amniotic fluid leakage might indeed result in long-term damage to the ears. However, little corroborating information can be found for this risk.  

Increased Admissions to Neonatal Intensive Care Units

Because of the risk for fetal respiratory problems and possibly also low-birthweight and prematurity, infants who have been exposed to amniocentesis may have a slightly higher rate of admissions to the NICU.  Sant-Cassia (1984) and Abboud (2000) found higher rates of prematurity, especially among babies with more amniotic fluid leakage.  Greenough (1997) found a higher rate of NICU admissions in babies who had been exposed to amniocentesis.  

The prenatal testing FAQ at states:

In addition there is a risk of about 0.5% of a baby with very low birthweight and of neonatal respiratory problems. There is a high incidence of feto-maternal bleeding.

Enkin et al. (A Guide to Effective Care in Pregnancy and Childbirth, 1995) writes:

A controlled trial of genetic amniocentesis in over 4000 women at low risk of an abnormality showed that the procedure was associated with a high incidence of fetomaternal bleeding, an almost threefold increase in the miscarriage rate, and, perhaps most noteworthy, a significant increase in the incidence of babies with very low birthweight and of respiratory distress syndrome.


Talipes Equinovarus, commonly called clubfoot, is a birth defect where the foot is deformed and turns abnormally to the side. A picture of what a clubfoot looks like can be found at

Although it can have a number of far more common causes, clubfoot may also be associated with amniocentesis, especially Early Amniocentesis. The speculation is that by removing amniotic fluid during a critical period of fetal development, the baby may not have enough fluid to suspend it comfortably in utero, and abnormal pressure may be placed on delicate forming bones and tissues, thus causing a clubfoot.  

Although amniotic fluid is generally replaced within hours to days after an amnio, in some women it may take longer or the fluid replacement may not happen adequately because of some unknown factor.  In these babies, orthopedic problems like clubfoot may occur.  

According to recent research (Lancet, 1998), the risk of clubfoot is greatly increased with Early Amniocentesis.  In this study, the risk of clubfoot was increased ten-fold after early amniocentesis (from 0.1% after second trimester amniocentesis to 1.3% after early amniocentesis).  

Although some research has found a higher rate of clubfoot or other orthopedic abnormalities even in second trimester amnios, The March of Dimes states that the risk for clubfoot after second trimester amniocentesis does not differ from the underlying rate of clubfoot in all US babies.  

Rh Sensitization

There is a small chance that the mother can be exposed to fetal blood or cells in the process of an amniocentesis.  In an Rh negative mother with an Rh positive baby, this may sensitize her to the baby's blood and cause her to develop antibodies.  This will not harm the baby of that pregnancy, but it may harm a future Rh positive baby.  

This problem has been found in some past research but the risk of Rh sensitization seems small.  Still, it is routine nowadays to automatically give Rhogam immunoglobulin after amniocentesis to Rh negative mothers as a precaution.  However, notes that Rhogam "will not protect women from being sensitized to more rare antigens such as Kell." 

So while Rhogam may be protective against some sensitization issues, it will not protect against them all.  Still, it seems a sensible precaution in women who are Rh negative (with Rh positive partners) and planning more children.  Some types of Rhogam are available without mercury or other preservatives; if you plan to have an amnio and will receive Rhogam, you might want to look into the various types available carefully.


If the placenta is perforated, it is possible that this could cause a hemorrhage, although recent research seems to indicate that placental perforation is not as risky as once thought.  

If the vessels of the umbilical cord are perforated this can cause fetal hemorrhage, which of course could be very serious.  There are a few (and fortunately rare) case reports of fetal bleeding and even fetal exsanguination (bleeding out) and death after amniocentesis. 

With continuous ultrasound guidance, hemorrhage is very rare nowadays. Still, it remains a small but potentially serious risk in amniocentesis.

Fetal Damage

As noted, in the past amnios were done without continuous ultrasound monitoring.  The amnio was either done totally "blind", or ultrasound was used to note where the baby and placenta were, then the ultrasound was stopped, and the needle was inserted based on those findings (no continuous monitoring).

The problem with this is that babies move, especially in response to maternal stress or pain! Some babies unfortunately moved into the path of the needle, and were sometimes nicked.  Amnios in the 1970s reported a fetal injury rate of 1-3% (Karp and Hayden, 1977) or even up to 9% (Epley, 1979).  Most were "cutaneous" (skin) injuries, but occasionally more serious damage resulted. 

In a few cases, the medical literature records very serious damage or even death in the fetus from amniocentesis as it was practiced then. There are reports of ocular trauma, intestinal atresia, fetal exsanguination, and other horrifying damage to babies.

Once continuous ultrasound monitoring began to be used, however, the doctor was usually able to compensate for any movement from the baby.  The needle could be repositioned as needed, or if necessary, pulled out entirely and reinserted in another location.  Continuous monitoring significantly lowered the risk associated with amniocentesis.  It has offered great benefit during amniocentesis, which significantly outweighs any potential risk associated with prolonged use of the ultrasound.  It is definitely a very necessary part of modern amniocentesis. 

However, even continuous ultrasound monitoring cannot eliminate all risk of fetal damage.  Although rare, resources do document that occasionally, there can still be:

slight dimpling of the skin where the baby was poked during the procedure, and very rarely, a baby may die (as quoted from the amniocentesis FAQ at ).  

Another possible source of fetal damage from amniocentesis may be through "Amniotic Band Syndrome."  In this, the inner sac of waters are thought to rupture, and fibrous "strings" of amniotic sac material drift through the fluid.  Usually this is harmless, but sometimes these "strings" rest against the baby, restraining certain body parts, and over time may even restrict the growth of certain parts of the fetus.  

Some babies with Amniotic Band Syndrome are born with scars and creases in their bodies, parts of their body stunted in growth, or in rare cases, limbs that have been amputated in utero by these "strings."  One recent case report discussed a case of Amniotic Band Syndrome where the amniotic band constricted the baby's umbilical cord and the baby died (Strauss 2000).

Although most cases of Amniotic Band Syndrome have nothing to do with amniocentesis, a few may be associated with it.  For example, in the case report cited above in which the baby died after umbilical cord restriction, the amniotic band was apparently caused by a second trimester amniocentesis, and the authors caution that invasive prenatal testing may induce rare complications like this. 

Although fetal trauma from amniocentesis is rare nowadays, it is not a risk that can be completely eliminated.


Accuracy of Amniocentesis

So how accurate is amniocentesis anyhow?  What conditions does it test for?  What conditions does it not detect?  Do "normal" results guarantee a healthy baby?

What Conditions Amniocentesis Can Detect Accurately

Amniocentesis is very good at picking up most chromosomal birth defects, such as Trisomies (3 chromosomes instead of a pair, such as Down Syndrome [trisomy 21]), translocations (where part of one chromosome has been relocated to the 'wrong' place), and other chromosomal problems. 

Amniocentesis can also detect many genetic problems as well, but only if it is looking for them.  The FAQ on amniocentesis states that more than 100 inherited diseases can be detected through analysis of the amniotic fluid. If you are a carrier for a genetic disease like Tay-Sachs or Cystic Fibrosis, an amnio analysis will be targeted to look especially for those diseases. Otherwise, many amniocentesis analyses will not look specifically for these problems.

Amnios can also detect Neural Tube Defects by testing Alpha Fetoprotein and Acetylcholinesterase (AChE) levels in amniotic fluid directly.  Because it is a direct measurement (instead of an indirect measurement of fetal AFP levels in maternal blood), this may be even more accurate than maternal serum AFP/Triple Testing.  Some resources indicate that it is indeed more accurate----but at a greater risk to the infant.  Other resources feel that AFP measurements from amniotic fluid are an outdated test and should be dropped.

When looking for specific disorders such as Neural Tube Defects or Down syndrome, amniocentesis can be a very useful and accurate test.  According to the website,, if the amniotic fluid AFP is normal and the accompanying ultrasound shows a normal spine and abdominal wall, "Spina bifida or abdominal wall defects can be excluded with 99% certainty.  Down syndrome is excluded with 99% certainty as well if the chromosomes are normal."

According to the March of Dimes:

More than 95 percent of the high-risk women who have prenatal diagnosis receive reassuring news that their unborn babies do not have the disorders for which they are tested.  However, no one prenatal test can guarantee the birth of a healthy baby, since only some birth defects can be ruled out before birth.  Three to four out of every 100 babies have a birth defect.

Amniocentesis has an accuracy rate of between 99.4 and 100 percent in diagnosing chromosomal abnormalities.

What Conditions Amniocentesis Does Not Detect

Of course, not all birth defects are chromosomal.  Amniocentesis will not detect structural or developmental problems like heart defects, clubfoot, cleft palate, hypospadias, or congenital hip dislocation. Problems caused by exposure to toxic substances will also not be detected by amniocentesis.

In addition, because most amnios do not specifically look for genetic diseases unless specifically ordered to do so, amniocentesis will not detect most genetic diseases.  Most labs can detect chromosomal disorders, but relatively few are able to do genetic analyses.   If you know you want to have a genetic analysis done, your test will be more expensive and take much longer.  

According to, there is a three percent chance of serious birth defects that will not be detected by amniocentesis.  In addition, they stress that "Amniocentesis cannot guarantee the birth of a perfect baby."

Potential Sources of Error

In any lab test, there is a small chance of a lab error.  One mother in The Tentative Pregnancy was told that lab errors occur about once in every thousand amnios.  Of course, that's a good rate-----unless YOU happen to be the one the error is made with.  Remember, on the basis of this lab report may hang a baby's life.  Thus, lab errors, while rare, can be devastating.

Another possible source of error is if the lab cultures the mother's cells by mistake instead of the baby's.  This would require a repeat amnio to be performed a few weeks later, which of course causes a lot of problems if the parents would consider abortion in case of a birth defect.

Another problem can include "pseudo-mosaicism". According to

Occasionally the 'cultured' or 'grown' cells develop subtle changes from the original cells. This makes the chromosomes have a slightly different configuration and appearance, artificially creating different cells called 'pseudo-mosaics'. It is impossible to interpret these cells, making the results of the amniocentesis inconclusive and the amniocentesis would need to be repeated or a cordocentesis may be considered.

Amniocentesis for other purposes can be subject to errors as well.  As noted, amniotic fluid taken during a midtrimester amnio is tested for AFP levels in order to check for Neural Tube Defects.  However, fetal blood in amniotic fluid can falsely increase AFP levels, making it look like a Neural Tube Defect is more likely.  If an amnio is being done to check on fetal lung maturity, blood or meconium in the fluid can produce a false L/S ratio.  

So while amniocentesis is usually accurate, occasionally some factors can influence the test and cause errors in lab results.

Ambiguous Diagnoses

Another potential problem rarely mentioned by amnio resources is ambiguous results.  The FAQ on amniocentesis acknowledges this potential problem, noting: 

There are also some results which are inherently ambiguous, because we don't really know the effect of the chromosomal abnormality detected. Trisomy 21, or Down syndrome, is a well-defined syndrome (although, even there, amniocentesis will not tell how severe a case of Down syndrome the baby will have), but the results of sex chromosome trisomies are less well known. Is XYY associated with more violent behavior or isn't it? Some reports say yes, others no. The effects of XXX are also unknown. 

Barbara Katz Rothman also discusses the problem of ambiguous diagnoses in her book, The Tentative Pregnancy.  She notes that sometimes it's hard for lab techs to interpret chromosomal patterns, and sometimes results are not clear.  She states, "Laboratory errors do occur, and not all chromosomal patterns look like they have come out of the textbook.  The results cause stress, and may raise more anxiety than can be alleviated with further testing."

Katz Rothman tells the story of one woman who was told that the baby had a "twist" on one chromosome.  A "twist" is a translocation, or as Katz Rothman explains it, "The chromosomes are all there and accounted for, but things may not be in the right order."  The lab asked the parents to have their chromosomes tested, and the mother was found to have this same "twist," and since the mother seemed healthy, the baby was assumed to be healthy as well. However, doubts had been planted in the mother's mind, and she remained uneasy and full of fear.

Another woman in the book was tested for age-related Down Syndrome risk.  She was told that the baby has an extra chromosome 8, but that that was so rare the results were more likely to be a lab error.  They did a repeat test, which found no trisomy on chromosome 8, but they couldn't promise her that the baby did not have mosaicism----where some cells in the child have trisomies and some do not.  So again the seed of doubt and worry was planted, and the mother found it impossible to be at peace about her baby's health, even well after it was born, seemingly healthy.  She wrote, "It's really hard.  I wish I never had an amniocentesis in the first place."

In a newspaper article in 2002, one father spoke of his experience with ambiguous diagnosis.  His wife had an ultrasound and amniocentesis at 17 weeks. The ultrasound showed the baby not growing as fast as expected, with less fluid and a larger placenta than expected. The parents had many repeated ultrasounds over the next five weeks, some of which had differing results, both better and worse.  The parents agonized over their decision for weeks.  No one could give them any firm answers.

In the end, after being told that the chances were probably very high that the baby would be born dead or in a vegetative state and that carrying to term might endanger the mother, the parents opted for abortion, but it broke their hearts. The father wrote, "This is the double-edged scalpel of reproductive science.  The technology that informs you your future baby is mysteriously endangered also makes him real, a boylike creature swimming in utero."  

Although most of the time, amnio results are fairly clear, sometimes there are ambiguous results, and the parents end up living in an inferno of indecision and unknowns.  Not knowing what to do while the pregnancy clock is ticking can be hell.   

Amniocentesis Cannot Guarantee a "Normal" Baby

Amniocentesis is not perfect.  It cannot detect all forms of birth defects or diseases.  Just because your amnio comes back as "normal" doesn't mean you are guaranteed a "normal" baby.  As noted above, there is still a fair chance that a baby can have other birth defects or a genetic disease.

Still, if you are greatly concerned about a chromosomal defect, certain genetic disorders, or Neural Tube Defects, an amnio is a pretty accurate way to determine the baby's status on these issues.  Unfortunately, it is not a risk-free way of doing that, and occasionally errors and ambiguous results do occur.  

Although parents and doctors like to think of prenatal testing as clear-cut and virtually infallible, it is not.  But it can be useful to some people, in some situations, to test for some conditions, with the understanding that the test is not perfect and can sometimes cause more worry than it relieves.


Choosing Whether Or Not To Do An Amnio

"The technology of prenatal diagnosis is usually presented to us as a solution, but it brings with it problems of its own...the technology of prenatal diagnosis has changed and continues to change women's experience of pregnancy."  

---Barbara Katz Rothman, The Tentative Pregnancy

One of the most difficult things about amniocentesis is choosing whether or not to have one.  It is one thing to consider this testing theoretically; it is another thing to consider doing it when you are pregnant and can already feel the baby moving.  Weighing the benefits and risks of amniocentesis is very complex and does not lend itself well to simplistic answers.  

The Implications of Amniocentesis

One excellent book that does a very good job of presenting the complexity of the prenatal testing issue (as well as the pros and cons of various prenatal testing technologies) is The Tentative Pregnancy by Barbara Katz Rothman.  One of her most important points is that parents need to think thoroughly about all of the implications of prenatal testing before they make decisions about it, and consider the subtle ways in which prenatal testing can affect the way they think about the pregnancy and the baby.

Most people sign the form agreeing to an AFP test, an ultrasound, or an amniocentesis without really thinking these issues through.  Because most of the time the answers that come back are reassuring, most parents are spared from having to really consider the tough choices.  But inherent in prenatal diagnosis are the most difficult issues of all, those of abortion, eugenics, attachment, and unconditional vs. conditional love.

There is no one wrong or right answer about amniocentesis.  Answers will differ between couples, and different medical circumstances will change the risk/benefit ratio associated with amnios. Each couple must make this decision for themselves, but it is important to FULLY consider all the implications of the test before choosing.

The Abortion Dilemma

Inherent in any testing for birth defects is the subject of abortion, whatever you think of that difficult topic.  The stark reality is that most of the time when an abnormality is found, the baby is aborted.  Many people choose prenatal testing with the idea of abortion in the back of their heads, although sometimes only for certain conditions. Even those who go into the testing feeling like they would not choose abortion often do end up choosing abortion anyhow if a problem is diagnosed.  

Although the ultimate choice is of course up to the individuals involved, there is a great deal of strong pressure for women with "abnormal" fetuses to have an abortion.  Doctors usually assume that of course a woman who has a fetus with a birth defect is going to terminate the pregnancy.  Although officially they state that these tests are for information only, unofficially women report subtle but very significant pressure to abort a pregnancy with abnormalities.  

However, some couples choose amniocentesis even after firmly deciding that they would never choose abortion, no matter what the results are.  In these couples, the desire to know of problems ahead of time so they can be more prepared outweighs any potential risk for miscarriage with the procedure.  Other couples get a non-reassuring test result from an AFP test or ultrasound, and even though they would not choose abortion, choose to have an amnio because they cannot stand the suspense of not knowing.  They feel they have to know if the baby has problems, once the question has been raised in their minds.

That abortion stands hand in hand with prenatal testing creates enormous conflicts for parents.  Most begin the prenatal testing process with seemingly benign tests like ultrasounds and the AFP/Triple Test, usually without fully understanding that the logical end of such testing may well be a decision about abortion.  Those who enter the testing process naively often end up disillusioned and traumatized by the difficult nature of such decisions, forced upon them in a very short period of time. 

It is very important that couples consider the FULL scope of possible decisions before entering into prenatal testing, and that includes their feelings about abortions and disabilities.

Evaluating Disabilities and The Eugenics Dilemma

Another major problem with amniocentesis is evaluating your own feelings about various disabilities, making judgments about when life is not worth living, and deciding how much perfection is required to love and keep a child.  Katz Rothman describes this:

When people seek prenatal diagnosis, they are entering into a process of evaluating disabilities, deciding which disabilities make life not worth living for the disabled person, and also which disabilities demand too much or are beyond their competence as parents.  Individual women entering the process may or may not fully anticipate how difficult these decisions will be.  Most are not informed enough to anticipate the range of possible diagnoses, or the ambiguity inherent in the diagnostic process. 

Many doctors view prenatal diagnosis backed up by abortion for disabilities as appropriate usage of resources, since the parents, the state, and medical insurances no longer then have to care for this child and its lifelong medical bills.  Disabled people would not agree.  Most are incensed at the thought that others would judge their lives as 'not worth living' because of their disability.

Families of those with disabilities are often caught in the middle.  Most love their disabled children fiercely and are outraged at the suggestion of abortion for disabilities.  However, the unpleasant truth is also that some disabilities are severe and overwhelming, that taking care of a severely disabled child is a life-long task, and that the financial and emotional burdens can be overwhelming. 

Some parents of disabled children choose amniocentesis with their next pregnancy because they cannot countenance the possibility of taking care of another disabled child. Others choose amniocentesis because they want to know ahead of time so they can prepare, but would never consider aborting, no matter what. Others choose no prenatal testing because they feel a child---any child---is a gift, and they choose to omit prenatal testing so that they can appreciate the child for what it is instead of worrying about what it isn't during the pregnancy.  There are no easy answers on these choices.

Remember also that amniocentesis cannot determine the severity of a disability, merely the presence of it.  Some children with Down Syndrome are severely retarded, some only minimally.  Some have severe health problems, others lead fairly normal lives.  Some end up institutionalized, and some learn to read and write and hold a job.  An amniocentesis diagnosis of Down Syndrome will not be able to tell you where your child will fall within this range of variation. 

Some children are born with devastating birth defects or diseases that guarantee a short life full of suffering.  Because these children often suffer great pain and agony before they die, is it more merciful to end their lives sooner rather than later?  Or is that playing God? These are among the most difficult of choices that parents can face.

Sometimes, ambiguity in diagnosis causes difficult dilemmas.  There are certain chromosomal differences where no one is sure how meaningful the diagnosis is.  For example, extra or missing sex chromosomes (the "x" and "y" chromosome) are common, but their meaning is unclear at this point.  Some people have an extra "twist" or translocation of their chromosomes; no one really understands yet whether this really affects them or not.  Because children with some "minor" chromosomal problems may or may not develop problems later on, is this worrisome enough to have an abortion?  

Deciding where to draw the line about disabilities and birth defects encroaches on the difficult territory of Eugenics.  As Katz Rothman puts it:

The history of prenatal diagnosis has roots in the eugenics movement, in various attempts to "improve the race."  It is certainly one of the less flattering lights in which to view prenatal diagnosis, but part of its history has been an attempt to control the gates of life: to decide who is, and who is not, fit to make a contribution to the "gene pool."

Central to the whole issue of Eugenics are many thorny ideas, including: 

The Tentative Pregnancy

Another problem with prenatal testing is that it puts women in limbo when it comes to announcing their pregnancies and bonding with their babies.  For good or ill, it changes the way they experience pregnancy.  

Barbara Katz Rothman discusses this issue at length in The Tentative Pregnancy.  She states:

Seeking and waiting for information changes the pre-information stage of pregnancy, creates what I think of as a "tentative pregnancy."  It incorporates the issue of abortion right into the route of motherhood and institutionalizes conditionality in mother love....

The new technology of reproduction puts many women into a difficult social state...A woman's commitment to her pregnancy under the conditions imposed by amniocentesis can only be tentative.  She cannot ignore it, but neither can she wholeheartedly embrace it....

Most women manage to keep the anxiety under control, but there is a cost to that.  The cost is in the developing relationship with the fetus.  Distance must be maintained....

[Prenatal testing] changes the meaning of pregnancy, and of the mother-fetus relationship, for the mother.  A diagnostic technology that pronounces judgments halfway through the pregnancy makes extraordinary demands on women to separate themselves from the fetus within...Only after an acceptable judgment has been declared, only after the fetus is deemed worthy of keeping, is attachment to begin.  

What does it do to motherhood, to women, and to men as fathers, too, when we make parental acceptance conditional, pending further testing?

For some women who choose prenatal testing, early pregnancy becomes a time of suspended animation whose effects showed in subtle but telling ways.  Katz Rothman found that this group reported  feeling fetal movement later than women who do not choose amniocentesis, and many of them did not wear maternity clothing until after the results of the amnio were back.  This speaks of a delayed bonding and postponed attachment.  What does that do to the fetus within, and what does that do to the mother who must, on some level, deny her connection to the child within?

Women are being asked to take care of themselves and their pregnancies, while knowing full well that at some point, they may choose to end that pregnancy.  This kind of "conditional" love takes a difficult toll, and one not easily resolved.  

Some parents prefer to know about any problems ahead of time so that they could grieve these problems sooner rather than later and be more prepared for the baby's situation at birth.  On the other hand, some parents do not feel that knowing ahead of time was a gift at all. Katz Rothman talked to many parents who felt like their experiences of pregnancy and birth were tainted by foreknowledge of the baby's problems, and that knowing of even very minor problems took much of the joy and anticipation out of their pregnancies.

For example, one case presented in The Tentative Pregnancy tells of a woman who was told that her female fetus was missing one X chromosome on some of her cells but not on others, and that as a result she might have Turner's Syndrome, either in the full-blown or mosaic form.  The parents were unable to find much information on Turner's Syndrome at the time, nor what it would mean to have only some cells missing the second X chromosome (mosaicism).  While they were trying to figure out what the diagnosis meant, the mother reported that she felt distant and alienated from her baby.  She recalled:

Initially I felt this alienation---from the pregnancy, from...the fetus.  I didn't want to put my hands down on my stomach.

Oftentimes, this alienation takes much of the joy of pregnancy away, and the parents spend the whole time in a state of great anxiety.  This state often extends beyond the prenatal period too, with parents reporting feeling more alienated from the child after birth.  

When the focus is only on the child's potential problem, there is no time to enjoy the pregnancy, nor to enjoy the child simply as a child.  Prenatal testing can take that simple enjoyment of the child for its own sake away, and that can be a very profound loss for parents. 

Thus, while amniocentesis can be a very useful test, it can also be a double-edged sword.  Katz Rothman writes:

While we must acknowledge the relief and reassurance that amniocentesis provides, it is important to place that in the context of the anxiety it generates.

For some women, prenatal testing means waiting to bond with their child until after they find out the fetus is free of the most common birth defects.  It means living in a state of limbo, emotionally neither totally pregnant nor not pregnant.  Even those who would not abort say their experience of pregnancy was not the same while they were awaiting the results of prenatal testing, or if they found out that something "might" be wrong.

Most of the time, knowing about a birth defect ahead of time does not result in prenatal cures or make any difference in birth choices.  Does the foreknowledge of problems really help?  What do you do once you know there's a problem?  How do you make those kinds of terrible choices?  Even if you do nothing, what kind of emotional price do couples pay in worry, and in having much of the joy of the rest of their pregnancy taken from them?  This is the double-edged sword of prenatal testing.


Making The Amniocentesis Decision

Choosing whether or not to have an amniocentesis is obviously a highly personal decision.  Some people decide against having an amniocentesis (or any prenatal testing) no matter what, while some choose amniocentesis even when they are considered "low risk" for birth defects.  Many women choose limited prenatal testing and have an amnio only if other tests indicate a potential concern.  

Some choose amniocentesis only if they are over 35, while others choose elective amniocentesis even well before 35.  Some couples choose amniocentesis with the intention of aborting if there are any "abnormal" results, while others would choose abortion only for certain birth defects or diseases but not others.  

Still other people choose amniocentesis even when they know they would never choose abortion.  In these cases, parents might wish to know of any serious problems ahead of time, especially in the unusual cases when in-utero treatment might be available, or where changes in birth decisions might be helpful.  

Amniocentesis is an extremely personal decision, and it is not the intention of this FAQ to promote one decision over any other, only to raise questions and fully explore all the implications of amniocentesis.  

When considering the amniocentesis question, take some time to review your own personal values, consider possible reasons for and against amniocentesis, answer some provocative questions about amniocentesis, and explore various scenarios you might encounter BEFORE you make your decision for or against.

Personal Values and Amniocentesis

Obviously, personal values deeply affect a person's decisions about amniocentesis.  A person who believes that abortion is wrong under any circumstance is going to be much less likely to do an amnio, although sometimes there may be reasons to do one even if you would not abort.  Conversely, couples who are genetically at risk for a child with severely debilitating diseases may feel that the burden of long-term care blurs the ethical questions of amniocentesis and are generally highly likely to choose one.   

There are other ways in which personal values can influence the decision to have an amnio as well.  As Dr. Marjorie Greenfield states at

At 35 years old, women have a risk of about 1 in 200 of giving birth to a baby with Down Syndrome.  In the United States, the standard is to offer amniocentesis to all women who have more than a 1 in 200 chance of identifying a genetic problem in the fetus, that is, when the risk of Down Syndrome equals the risk of causing a miscarriage with the amniocentesis.  

Of course, this represents a value judgment that does not hold for all families.  For some, any risk of Down Syndrome feels unacceptable, and they choose to have amniocentesis even though the risk of the test causing a miscarriage is higher than the risk of Down Syndrome that the test might detect. 

For others, the risk of causing the loss of an otherwise healthy pregnancy feels unacceptable, and they choose to decline amniocentesis, even if they are at high risk of finding a problem.  This is often the case with older moms who have gone through infertility treatment, who feel they cannot risk losing the pregnancy under any circumstances.

Most of the time when there is a problem diagnosed prenatally, there is nothing that can be done differently to improve a baby's prognosis.  You find out there's a problem but that there's little that can be done.  What then?  This is one of the difficult dilemmas presented by prenatal diagnoses, and this is where clarifying your own personal values ahead of time can be helpful:

These are the personal values that will influence choices about amniocentesis. Sit down with your partner and think about the possible scenarios you might face and your opinions on the questions above.  

Looking For Guarantees Where There Are None

One of the dangers of prenatal testing is that parents begin looking for a guarantee that their child will be perfect.  Some parents see prenatal testing as a way to help take some of the uncertainty out of life.  But that is an illusion in many ways, as Katz Rothman brutally points out:

An irony in all this is that the technology still cannot guarantee a "blue ribbon baby."  A fetus can pass all of the tests and still be far from perfect at birth.  A child can be born or become retarded, disabled, disfigured from thousands of causes...There are limits to control, and our children are always "hostages to fortune"...The possibility of spending the rest of one's life caring for a sick or disabled child can never be eliminated by prenatal testing...Motherhood is, among other things, one more chance for a speeding truck to ruin your life.

Prenatal testing can take some of the uncertainty out of your life, but at what price?  And are you comfortable with that price?  That is the question you have to ask yourself.  

Advanced Maternal Age: Amniocentesis Is Not Mandatory

Due to the increased risk of miscarriage, amnios for detection of birth defects are not recommended for the general population until the mom is at least age 35, because at that point, the theoretical risk for miscarriage approximately equals the increased risk for having a baby with Down Syndrome.

However, if  there are special circumstances like a family history of birth defects or an abnormal prenatal screening test, there will be significant pressure to do an amnio in a mother who is not yet 35.  And of course, at any age, if you would like to have an amnio, you can request one, and that request is usually honored.  

While the risk of birth defects does increase with age, these risks can be overemphasized. The odds of having a healthy baby are still in your favor even well into your 40s. The risk of a baby with Down Syndrome is generally cited to be about 1 in 100 or so at age 40.  If someone told you that you had a 99/100 chance of winning the lottery would you feel confident about your chances?  It's the same for having a "normal" baby.  Your odds are still 99/100 that the baby will be "normal" when you are 40.  Although the odds do change over time, even well into your 40s the odds are still in your favor that you will not have a baby with Down Syndrome.

Do not assume that you must have an amnio if you are over 35 or for any other reason. Doctors often automatically assume you will have an amnio if you are 35 or over; many hand you the paperwork without question at the first prenatal appointment.  However, any and all tests are always OPTIONAL; you do have the right to refuse them if you wish, no matter what your age.  

If you feel unduly pressured towards an amnio because of your age, this is often a sign that you need to switch providers because they already perceive you as "high risk" due to your age, and they already obviously tends towards considerable intervention. If the doctor's emphasis on your age or pressure for prenatal testing makes you uncomfortable, this is a strong indication that this is not the right provider for you. 

Amnios are an effective tool under certain conditions but should not be used routinely because of age or any other condition (including size). No doctor should pressure a woman into an amnio simply because of her age or other factors. They can suggest the advisability of an amnio, but the choice is ultimately up to the parents involved, not the doctor, and if the doctor can't live with that, he is not the doctor for you.  

Personal beliefs should play the biggest role in your decision about amniocentesis, much more than any supposed "risk factor" like age. Be sure to discuss thoroughly all aspects of the decision and the procedure with your health care provider.  It is not a decision to make lightly or routinely, and certainly not just because of age or any other risk factors.  

Dealing With Pressure About Amniocentesis

Sometimes parents encounter a great deal of pressure about amniocentesis and other prenatal testing decisions. Sometimes this pressure comes from friends and family, but more often it comes from medical personnel.  At other times, parents feel pressure not to have prenatal testing, even when they feel strongly they want to have it.  

If you have weighed all the potential benefits and risks and feel that amniocentesis is the right decision for you, proceed with the decision.  No one else has the right to dictate your choices to you.  Rest assured that it is usually fairly easy to find a doctor to support you in these choices (or you can switch in order to find one who is supportive).  

However, it is more common for parents to be pressured  into having an amnio, usually by medical personnel.  Many feel that amniocentesis should be required (or at least strongly promoted) among women deemed to be more "at risk" for certain conditions, even when that overall risk is still quite low.  Women who are older than 35, women who are plus-sized, women who have certain medical conditions (diabetes etc.) often face tremendous pressure to have an amniocentesis. 

Many women who are "more at risk" do decline extra testing, and there are good arguments for doing so.  Being at a slightly higher risk for a condition does not mean the condition will occur, nor does it make prenatal testing mandatory or even a good idea for everybody in that group.  Testing should be offered, not required, and providers need to offer those choices without pressure or judgment.  

Sometimes, providers apply a great deal of pressure to have extra testing or don't want to respect your reservations about testing decisions. Some will even classify you as "high risk" if you decline testing!  If at any time you feel your provider is greatly pressuring you towards an amnio or other prenatal testing you don't want, SWITCH PROVIDERS!!  

If your provider treats you as high risk and greatly pressures you for or against any particular test, you should ask yourself whether that person is the right provider for you.  Many women choose to switch providers when they encounter one who does not respect their right to make their own prenatal testing decisions.  Often, this is the sign of a highly interventive provider, and one you are probably better off without.  

As for friends and family, remember that you do not have to keep other people informed about your prenatal testing decisions in any way.  It is your own business, and if anyone questions you about it, politely but firmly tell them that you are considering your choices but that your decision will remain private. 

If You Would Not Terminate a Pregnancy, Why Consider Amniocentesis

One common argument against amniocentesis is that if you would not consider abortion based on its findings, why do the test and expose the child to the risk of miscarriage?  This is a valid argument, and one reason many couples do not choose amniocentesis.  

However, some couples still choose amniocentesis even when they would not choose to terminate a pregnancy.  In this situation, these couples feel that they would prefer to know about any problems ahead of time, so they could adjust before the baby was born.  

These couples often feel it is best to know about problems ahead of time so they can discuss the problem with genetic counselors and health care providers.  They may feel that knowing ahead of time would give them time and space to become more informed about the baby's problem, to grieve the loss of a "normal" child, and to be more ready to welcome that unique baby into the world at his birth.  According to Katz Rothman, some research supports the idea that knowing ahead of time can help parents adjust better and be more prepared; some does not.

Another argument for choosing amniocentesis even when abortion would not be chosen is that in rare cases, knowing ahead of time of a certain fetal condition can improve outcome.  In some cases, different birth choices may be more optimal if a birth defect is known about ahead of time.  For example, it is thought that some cases of spina bifida may be more safely delivered by cesarean.  Or doctors may know to watch for certain complications during labor and birth if they know about certain birth defects ahead of time.

Another argument for knowing about problems ahead of time is that specialists can be brought in for immediate neonatal care after baby is born.  This may be especially helpful in certain defects like heart problems.  ( There is more information on this at, and also at and

Other problems may not be readily treatable but doctors will know ahead of time to watch for problems, beginning right at birth.  Sometimes it's helpful to know of potential problems so the couple will know to deliver in a hospital that has a Level III Neonatal Intensive Care Unit.  

There are also a few conditions for which there are treatments in utero.  For example, the March of Dimes notes that two life-threatening inherited disorders of body chemistry, biotin dependence and MMA (methylmalonic acidemia), can be detected by amniocentesis and successfully treated in the womb.  

On the other hand, a problem diagnosed prenatally may sometimes worsen outcome instead of improving it.  The provider's perception of the pregnancy and the baby changes, and some research (see shows that babies diagnosed with problems prenatally by ultrasound  were delivered earlier and by more cesareans than babies with the same condition not diagnosed prenatally.  This did not improve outcome, and may have worsened it.  So prenatal diagnosis may be a mixed blessing in some cases.

Also, not every couple feels that knowing ahead of time about a problem is worthwhile.  Some couples found that it changed the experience of pregnancy for them, usually negatively, as noted above.  One mother interviewed by Katz Rothman chose not to have amniocentesis because she felt knowing would limit her perceptions of her child, that the child would only "become" his or her disease to her.  She said:

Knowing...adds stress to the remaining gestation and does not give the parents the opportunity to see the whole child, the child who is more like other persons than unlike them.  The parent can only focus on what's wrong, not what's right about a child.

So knowing about a problem ahead of time, even if you would not abort, is not always a blessing either.  However, in rare cases, it may improve outcome to know ahead of time. Parents who would not abort but who are still considering amniocentesis need to balance the small chance that knowing might improve outcome with the chance that an amnio might cause a miscarriage.  They need to also consider what emotional toll knowing about a birth defect might have on their pregnancy and their bond with their baby.

If You Do Decide To Have An Amniocentesis

Katz Rothman has several suggestions for parents who have decided to go ahead and have amniocentesis and other prenatal testing.  These are only her suggestions; not everyone will agree.  If you disagree with some of them, please feel free to choose a different course than she suggests.

Katz Rothman suggests that parents go ahead and announce the pregnancy, not keep it secret until they have the results of the amnio. She believes it is more important that you go ahead and bond with the baby than hold off bonding until halfway through the pregnancy when you know that all is "well."  Even if you miscarry after an amnio or choose an abortion, you will still have to mourn the child you have lost.  She feels that to do that privately, without any acknowledgement of your pain and loss from those around you, is more difficult. 

She suggests that parents expect good news from the testing, since even the most high-risk parents have very good odds for receiving "good news."  She suggests going ahead with your plans as if the baby is fine and everything is "normal." Don't delay bonding with your child; chances are that everything is fine. Don't suspend your life, waiting for news about the baby.  Have the test if you want it but go live your life normally in the meantime. 

She suggests that women not ask for what they don't want to know.  If there is a specific type of birth defect that you don't want to know about, don't ask.  If you only want chromosomal analysis, don't ask for genetic analysis.  If you only want to look for certain diseases or problems, only ask for those results, not the full spectrum of problems that can occur.  If you don't want to know if the baby has mosaicism (some abnormal cells, while others are normal), tell them that.  If you want to have the full spectrum of tests across the board to look for any possible problem, accept that this increases the risk for ambiguous results. Be specific about what you want in your own mind, and to the medical personnel involved.

If there is a "bad outcome"----if you get news of a birth defect, if you lose the pregnancy to miscarriage after an amnio, etc.---she suggests that you need to go out and find support.  This support may not be from friends and family, but from whomever can listen to you and be non-judgmental and loving about your feelings.  She suggests finding other people who have been in the same position and truly understand this "new kind of grief."

Be careful who you tell that you are having an amniocentesis, both family and friends.  People often have very strong opinions about prenatal testing, birth defects, abortion, and eugenics issues.  If you share your plans, you may end up backed into a corner, harassed, or having your decisions questioned.  Announce the pregnancy but keep your decisions about prenatal testing to yourself and the few people you know who can listen and support you non-judgmentally.



There is no easy or automatic answer when making decisions about amniocentesis and other prenatal tests.  When deciding whether to have a test  detect fetal abnormalities, think over all these issues beforehand.  

A large part of the decision-making process about amniocentesis depends on your views of abortion, your views on disabilities and caring for a child with a birth defect, and your comfort level with the increased risk of miscarriage with the test. The decision is yours, and the fact that the decision IS yours brings with it new dilemmas and new levels of pain, whatever you choose.  

One of the biggest problems with prenatal testing is that doctors can diagnose more birth defects than they are actually able to treat.  This leaves parents with a terrible dilemma of what to do with the knowledge of a birth defect, and the unpleasant fact that prenatal diagnosis often changes the experience of pregnancy and takes much of the joy and anticipation out of it.  More information, gotten earlier, is not always an advantage. 

Should an amniocentesis discover an abnormality or potential abnormality, decision-making becomes even more painful.  This is an extremely difficult choice, and far beyond the scope of this FAQ to discuss thoroughly.  Kmom recommends the booklet, "Precious Lives, Painful Choices" for anyone facing a decision like this (see reference list).  

It is in the potential detection of fetal abnormalities that prenatal testing presents the most difficult dilemmas.  No one answer is "right" for every person or situation, and the choices are some of the hardest a person can ever face.  

That's why it is very important for couples to discuss the implications of prenatal testing before the process begins, and to fully understand the implications of their choices.  




A Guide to Effective Care in Pregnancy and Childbirth.  Enkin, M., Keirse, M., Renfrew, M. & Neilson, J.  3rd edition. Oxford: Oxford University Press.  2000. 

Superb review of childbirth issues and management controversies.  Extremely evidence-based, very fair and clear.  Highly recommended.

The Tentative Pregnancy: How Amniocentesis Changes the Experience of Motherhood.  Barbara Katz Rothman.  New York: W. W. Norton & Company, 1993.  Available from or or

An excellent overview of the debate over prenatal testing of all kinds, but especially amnios.  Represents multiple points of view fairly.  Author interviewed a number of genetic counselors, doctors and other health professionals, as well as parents who had been through prenatal testing.  Shares the stories of families who chose testing, who received reassuring and non-reassuring results, and the choices that they made.  Not an easy book to read but certainly one that anyone dealing with prenatal testing should read.

Precious Lives, Painful Choices: A Prenatal Decision-Making Guide.  Sherokee Ilse.  Maple Plain, Minnesota: Wintergreen Press, 1995.  Available from

An excellent resource for parents who have received non-reassuring test results and now face difficult choices about what to do next.  Written with great compassion and understanding.

Websites About Amniocentesis

General Websites About Prenatal Testing

Websites About Clubfoot (Talipes)

Websites and Resources About Down Syndrome

News Stories About Amniocentesis


Medical Journal Articles About Amniocentesis

General Information About Amnios

Tabor, A et al.  Randomised controlled trial of genetic amniocentesis in 4606 low-risk women. Lancet. June 7, 1986. 1(8493):1287-93.

Randomized, controlled trial of 4606 women without known risk of genetic disease (ages 25-34 years).  Spontaneous miscarriage risk was 1.7% in the amnio group and 0.7% in the control group (no amnio, only an ultrasound).  Risk factors for miscarriage included increased AFP levels before amnio, perforation of the placenta during amnio, and withdrawal of discolored amniotic fluid.  There was more amniotic fluid leakage in the amnio group afterwards but no more vaginal bleeding. Rate of postural malformations was the same in the 2 groups.  However, "Respiratory distress syndrome was diagnosed more often (relative risk 2.1) and more babies were treated for pneumonia (relative risk 2.5)." 

Morrow, RJ et al. Ultrasound detection of neural tube defects in patients with elevated maternal serum AFP tests.  Obstet Gynecol.  1991. 78:1055-7. [from abstract]

Found that high levels on the AFP maternal serum test were associated with an increased risk for miscarriage after amniocentesis.  A targeted ultrasound may be the better first choice to check for NTDs after a high AFP test.

Anandakumar, C et al. Amniocentesis and its complications. Aust N Z J Obstet Gynaecol.  May 1992.  32(2):97-9.

Study from Singapore designed to test whether an experienced operator influenced the incidence of complications with amniocentesis. Complications like fetal loss, blood-stained amniotic fluid, culture failure, multiple needle puncture, leaking amniotic fluid, fetal trauma, and error was less common in the group with more experienced operators. 

Baird, PA et al. Population-based study of long-term outcomes after amniocentesis. Lancet. Oct 22, 1994.  344(8930):1134-6.  

Studied 1296 cases where women has amniocentesis, and 3704 controls where amniocentesis was not used.  Followed up cases and controls for 7-18 years.  The offspring of women who had had amnios were NO more likely to experience hearing problems, learning difficulties, visual problems, or limb anomalies than those who had not experienced amniocentesis.  The one exception was a higher rate of hemolytic disease due to ABO isoimmunization.  

Gillberg, C et al.  Long-term follow-up of children born after amniocentesis. Clin Genet.  January 1982.  21(1):69-73.  

122 children were followed, 62 of whom had been exposed to amniocentesis in utero.  They were examined between 5-7 years of age.  No differences were found between pediatric or neurodevelopmental disorders, orthopedic abnormalities, or respiratory problems during the neonatal period. 

Sant-Cassia, LJ et al. Midtrimester amniocentesis: is it safe?  A single centre controlled prospective study of 517 consecutive amniocenteses.  Br J Obstet Gynaecol.  Aug 1984.  91(8):736-44.

517 consecutive patients having an amnio in one center were followed.  289 of these were compared with 289 matching controls with no amnios.  There was no significant difference in rates of fetal loss, perinatal mortality or vaginal bleeding between groups.  There was however an increased risk for preterm delivery.

Abboud, P et al. Amniotic fluid leakage and premature rupture of membranes after amniocentesis.  A review of the literature.  J Gynecol Obstet Biol Reprod (Paris).  December 2000.  29(8):741-745.

Reviews the medical literature on the rare complication of amniotic fluid leakage and premature rupture of membranes.  In 13 recent studies, found 280 cases of amniotic fluid leakage in 17, 186 amnios.  Risk was increased with early amnio (<15 weeks) and when the needle was inserted far from the placenta.  Noted that bedrest "gave good results."  However, "Significant loss of amniotic fluid compromises pregnancy...When amniotic leakage persists for more than two weeks, there is little spontaneous resolution.  The risk of pursuing the pregnancy should be discussed with the couple in this case.  Risks include respiratory disorders, skeletal malformations and premature birth. New techniques such as 'amniopatch' may play an important role in the near future."  

Finnegan, JA.  Amniotic fluid and midtrimester amniocentesis: a review.  Br J Obstet Gynaecol.  Aug 1984. 91(8):745-50.

"A review of experimental amniocentesis in animals suggests risks to limbs and structural changes in fetal lungs.  In humans, orthopaedic abnormalities and respiratory difficulties appear to be a risk of amniocentesis, and studies addressing these risks are also reviewed.  Continued investigation of risks from fluid loss at midtrimester amniocentesis is recommended."

Finegan, JA et al. Infant outcome following mid-trimester amniocentesis: developmental and physical status at age six months. Br J Obstet Gynaecol.  Oct 1985.  92(10):1015-23.  

91 infants whose mothers had had amnios were compared with 53 infants whose mothers chose not to have amnios.  "The results indicated that amniocentesis does not appear to influence infant mental and motor development, temperament, physical growth, or the risk of orthopaedic abnormalities.  However, amniocentesis is not entirely free of risk because several of the infants had needle marks."  

Finegan, JA et al.  Child outcome following mid-trimester amniocentesis: development, behavior, and physical status at age 4 years. Br J Obstet Gynaecol.  Jan 1990.  97(1):32-40.

88 children whose mothers had had amnios were compared with 46 children whose mothers did not have amnios.  "The results suggest a wide range of developmental and behavioral variables studied is not influenced by removal of amniotic fluid in the mid-trimester. However, mothers who had amniocentesis were more likely to report a history of ear infections in their child...In support of this finding were the results of audiological assessment which demonstrated a trend toward a higher rate of bilateral middle-ear impedance abnormalities in children whose mothers had amniocentesis...Further study of the upper respiratory system is recommended to explore potential long-term sequelae of mid-trimester amniocentesis."

Finegan, JA et al.  Children whose mothers had second trimester amniocentesis: follow-up at school age. Br J Obstet Gynaecol.  March 1996.  103(3):214-8.

Same sample of children (86 exposed to amnios, and 44 controls this time) were examined at school age. No differences between groups were found.  "Second trimester amniocentesis does not appear to compromise child development, behaviour, growth or health."

Greenough, A et al. Invasive antenatal procedures and requirement for neonatal intensive care unit admission. European Journal of Paediatrics. 1997.  156: 550 - 52.

NICU admissions are increased in babies who have been exposed to amniocentesis. 

Amnios and Miscarriage

Papantoniou, NE et al. Risk factors predisposing to fetal loss following a second trimester amniocentesis.  BJOG.  October 2001.  108(10):1053-6.

Greek study that found that several factors seemed to be related to an increased rate of fetal loss following a second trimester amnio.  Women older than 40 years had about twice the fetal loss rate of younger women.  Women with a history of vaginal bleeding in the current pregnancy had 2.4x the risk for fetal loss.  Women with a prior history of 3+ first-trimester abortions or a second trimester miscarriage or abortion had an even higher risk for fetal loss (3.03x the risk).  

Ropwe, EC et al. Genetic amniocentesis: gestation-specific pregnancy outcome and comparison of outcome following early and traditional amniocentesis.  Prenatal Diagnosis.  Sept. 1999.  19(9):803-7.  

Found that miscarriage rates after amniocentesis varied significantly by week of gestation.  Found higher rates of fetal loss in amnios performed at or after 19 weeks of gestation. Also notes that miscarriage can occur as long as 6 weeks after the amnio.

Suggests that women not be quoted one single rate of risk for miscarriage, but rather a range of possible rates, based on weeks of gestation when amniocentesis is performed and including cumulative rates that include fetal loss that occurs even after several weeks have passed after the amnio. 

Saltvedt, S and Almstrom, H.  Fetal loss rate after second trimester amniocentesis at different gestational age.  Acta Obstet Gynecol Scand.  Jan 1999.  78(1):10-4.  

Swedish study that found that earlier amnios were associated with a higher fetal loss rate.  Amnios that were performed between 13-20 weeks were studied; the fetal loss rate was highest at 13 weeks.  One-third of losses occurred within 2 weeks of the amnio, and the rest were within 7 weeks of the amnio, so obviously losses can and do occur even once the immediate period after the amnio has passed.  Abnormal color of amniotic fluid and leakage of amniotic fluid were "strong predictors of fetal loss."  Tranplacental needle insertion, on the other hand, did not increase the risk for loss.  

Marthin, T et al. Transplacental needle passage and other risk-factors associated with second trimester amniocentesis.  Acta Obstet Gynecol Scand.  Sept. 1997.  76(8):728-32.

Followed all pregnancies that underwent midtrimester amniocentesis over a 10 year period in one Swedish medical center, and the risk factors for pregnancy loss associated with amnios.  2083 pregnancies were considered.  "There was a slight but nonsignificant relationship between the degree of experience of the gynecologist and risk for pregnancy loss.  A more experienced operator used significantly fewer needle insertions...Multiple needle insertions were also associated with a slight, albeit nonsignificant, increase in incidence in fetal loss (3.8% after 3 or more insertions vs. 1.2% after one insertion).  No difference in spontaneous abortion incidence was found in patients having an anterior versus a posterior placenta, nor did transplacental needle passage increase the risk for pregnancy loss."

Cruikshank, DP et al.  Midtrimester amniocentesis.  An analysis of 923 cases with neonatal follow-up.  American Journal of Obstetrics and Gynecology.  May 15, 1983.  146(2):204-11.  

Study on amnios from the 1980s that found the risk of spontaneous abortion as a result of amniocentesis varied from 0.2% to 1.4%.    Stained amniotic fluid was associated with a much higher risk for fetal loss (29%).  Unexplained elevations of AFP were associated with a 38% risk for a low birth weight infant.  "The only neonatal complication associated with amniocentesis was an apparent marked increase in the incidence of lower-extremity orthopedic abnormalities."  

Shapiro, LR et al.  Immediate and unexplained fetal death during mid-trimester amniocentesis.  Prenatal Diagnosis.  April-June 1983.  3(2):151-4.  

Discusses "immediate and unexplained fetal death" DURING amniocentesis.  Surveyed US programs and found 5 cases from 7524 at 4 centers, a rate of 0.06%.  A "neurogenic mechanism is postulated."

McGahan, JP et al.  Ultrasound needle guidance for amniocentesis in pregnancies with low amniotic fluid.  Journal of Reproductive Medicine.  July 1987.  32(7):513-6.  

Discusses the use of real-time ultrasonography in helping during difficult amniocentesis cases.  Case reports of 6 difficult amnios in the presence of reduced amniotic fluid were discussed.  3 cases of very low fluid (oligohydramnios) were discussed (all 3 later resulted in fetal death).  3 cases where decreased (but not severely low) amniotic fluid was accompanied by maternal obesity were also discussed (outcomes were fine and reassured doctors there was a normal pregnancy).  However, one has to wonder about the wisdom of withdrawing amniotic fluid when low amniotic fluid is already suspected, and whether that played a role in the 3 deaths from oligohydramnios.

Amnios and Respiratory Problems

Annapoorna, V et al.  Evaluation of auditory system in preschool children whose mothers had mid-second trimester amniocentesis.  J Perinat Med.  1996.  24(3):207-12.

Singapore study of 59 children exposed to midtrimester amniocentesis, and 63 control children.  There was no significant increase in NICU rates, impairment of speech, language development, or auditory function in children exposed to amnios.  However, incidentally, the authors found an increased incidence of respiratory illness in the amnio group (57.6%) compared with the control group (30.1%) and called for further study of this finding.

Milner, AD et al.  The effects of mid-trimester amniocentesis on lung function in the neonatal period.  Eur J Pediatr.  June 1992.  151(6):458-60.

39 healthy full-term babies who had been exposed to mid-trimester amniocentesis had lung function tests, as well as 42 controls.  "Babies subjected to amniocentesis had a significantly lower dynamic compliance...and tended to have higher resistance compared to controls...This provides further evidence that mid-trimester amniocentesis does have an adverse effect on lung growth and development."

Hunter, AG.  Neonatal lung function following mid-trimester amniocentesis.  Prenatal Diagnosis.  July 1987.  7(6):433-41.

354 women who had midtrimester amniocentesis were matched with controls who did not have amniocentesis, in order to compare the neonatal respiratory status of their offspring.  "There was no evidence that the infants exposed to genetic amniocentesis were compromised."

Early Amniocentesis

CEMAT Group.  Randomised trial to assess safety and fetal outcome of early and midtrimester amniocentesis.  The Canadian Early and Mid-trimester Amniocentesis Trial (CEMAT) Group.   Lancet.  Jan. 24, 1998.  351(9098):242-7.  

*The* big study on early amniocentesis vs. second trimester amniocentesis.  Women were randomly allocated to early amniocentesis (11-12 weeks) or midtrimester amniocentesis (15-16 weeks).  11 mL of amniotic fluid were removed in EA and 20 mL in MA.  No more than 2 needle insertions were done on the same day.  Maternal and fetal health were assessed at 20-22 weeks and again 5 weeks after delivery.  

There were more losses in the EA group (7.6% vs. 5.9%), and significantly more clubfoot (1.3% vs. 0.1%).  There was more post-amnio fluid leakage in the EA group (3.5% vs. 1.7%).  "Our study shows that early amniocentesis is associated with an increased risk of fetal loss and talipes equinovarus [clubfoot]." 

Johnson, JM et al.  Technical factors in early amniocentesis predict adverse outcome.  Results of the Canadian early (EA) versus mid-trimester (MA) amniocentesis trial.  Prenatal Diagnosis.  August 1999.  19(8):732-8.  

Examined Early Amniocentesis vs. Midtrimester Amniocentesis.  Found a number of factors associated with higher fetal loss during EA, including increased Body Mass Index, higher parity, 'difficult' procedures, post-procedure amniotic fluid leakage, bleeding, maternal hypertension, etc.  

Early Amnios were associated with higher rates of fetal loss, clubfoot, failed procedures, multiple needle insertions, amniotic fluid leakage, and failed cultures. "Performing amniocentesis before 13 weeks gestation (EA) was the major predictive factor for adverse outcome.  These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype."  Also found a higher rate of problems in amnios at 14 weeks, even though that may not be technically considered Early Amniocentesis by many resources.

Thompson, PG et al.  Lung volume measured by functional residual capacity in infants following first trimester amniocentesis or chorion villus sampling.  Br J Obstet Gynaecol.  June 1992.  99(6):479-82.

Compared the incidence of respiratory problems and lung volume abnormalities  in babies who had had first-trimester amnios (n=74) or chorionic villus sampling (n=86).  Used measurements of "functional residual capacity." CVS was associated with a higher incidence of neonatal respiratory distress (7%) vs. early amniocentesis (0%).  However, both groups showed high rates of low functional residual capacity.  "Both amniocentesis and CVS performed in the first trimester of pregnancy may impair antenatal lung growth."

Yuksel, B et al. Perinatal lung function and invasive antenatal procedures. Thorax.  Feb 1997.  52(2):181-4.

Notes that second trimester amniocentesis has been associated with "an excess of perinatal lung function abnormalities."  Examined first trimester amnios and first trimester CVS.  Found that "Procedures performed in the first trimester were independently associated with a high airways resistance.  These results suggest that invasive procedures performed in the first trimester of pregnancy have an adverse effect on perinatal lung function."

Greenough, A et al.  First trimester invasive procedures: effects on symptom status and lung volume in very young children. Pediatr Pulmonol.  Dec 1997.  24(6):415-22.

Assessed the impact of first trimester CVS and Early Amniocentesis on respiratory morbidity in young children (1 year).  Functional Residual Capacity was also measured in 5 month old babies who were exposed to CVS or EA prenatally (and also in controls).  Found an excess of respiratory symptoms and chest-related hospital admissions in the EA group compared to the controls. Positive symptom status was related significantly to EA and CVS interventions, bottle feeding, parental smoking, family history of atopy (allergies), and immaturity.  "We conclude that first trimester procedures are associated with increased respiratory morbidity in very young children."

Tharmaratnam, S et al. Early amniocentesis: effect of removing a reduced volume of amniotic fluid on pregnancy outcome.  Prenatal Diagnosis.  Aug 1998.  18(8):773-8.

Discusses the theory that removing less fluid (about half of that removed during second trimester amnios) during early amniocentesis might help improve prognosis.  Suggests that fluid depletion from amnios may persist for 7-10 days, a significant departure from what most amnio literature says. By removing 7 ml they obtained a 3.8% miscarriage rate, a 2.7% respiratory difficulty rate at birth, and a 1.6% rate of "fixed flexion deformities," all at the price of a small increase in the incidence of culture failure (2.2%).   

Nikkila, A et al. Early amniocentesis and congenital foot deformities. Fetal Diagn Ther.  May-June 2002.  17(3):129-32.  

This study examined the rate of foot deformities after amnios done at 12-14 weeks; other studies have examined the rate of foot deformities in early amnios done before 13 completed gestational weeks.  Found a higher rate of foot deformities than they expected (odds ratio 1.74).  The rate of spontaneous miscarriages after the amnio was 1.8% and the rate of amniotic fluid leakage was 1.9%.  "There was a significant trend for all complications to decrease with increasing gestational age at amniocentesis."

Amniocentesis and Obesity

Johnson, JM et al.  Technical factors in early amniocentesis predict adverse outcome.  Results of the Canadian early (EA) versus mid-trimester (MA) amniocentesis trial.  Prenatal Diagnosis.  August 1999.  19(8):732-8.  

Examined Early Amniocentesis vs. Midtrimester Amniocentesis.  Found a number of factors associated with higher fetal loss during EA, including increased Body Mass Index, higher parity, 'difficult' procedures, post-procedure amniotic fluid leakage, bleeding, maternal hypertension, etc.  

Early Amnios were associated with higher rates of fetal loss, clubfoot, failed procedures, multiple needle insertions, amniotic fluid leakage, and failed cultures. "Performing amniocentesis before 13 weeks gestation (EA) was the major predictive factor for adverse outcome.  These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype."  Also found a higher rate of problems in amnios at 14 weeks, even though that may not be technically considered Early Amniocentesis by many resources.

Regarding obesity and EA, "Maternal factors found to be independently predictive of fetal loss included increased BMI...Increased BMI was also a predictive factor for a 'difficult procedure', which in turn was associated with an increased risk of fetal loss.  This implies that maternal obesity likely imposes technical challenges to the operator, increasing the probability of a difficult procedure and of post-procedure complications."

Because there was limited fetal losses in the later amnio group (MA), any potential association between obesity and fetal loss in the traditional form of amniocentesis was unable to be investigated.  

McGahan, JP et al.  Ultrasound needle guidance for amniocentesis in pregnancies with low amniotic fluid.  Journal of Reproductive Medicine.  July 1987.  32(7):513-6.  

Discusses the use of real-time ultrasonography in helping during difficult amniocentesis cases.  Case reports of 6 difficult amnios in the presence of reduced amniotic fluid were discussed.  3 cases of very low fluid (oligohydramnios) were discussed (all 3 later resulted in fetal death).  3 cases where decreased (but not severely low) amniotic fluid was accompanied by maternal obesity were also discussed (outcomes were fine and reassured doctors there was a normal pregnancy).  However, one has to wonder about the wisdom of withdrawing amniotic fluid when low amniotic fluid is already suspected, and whether that played a role in the 3 deaths from oligohydramnios.

Amniocentesis and Rh Sensitization

Hill, LM et al.  Rh sensitization after genetic amniocentesis.  Obstet Gynecol.  Oct 1980.  56(4):459-61.  

Early study of the problem of Rh sensitiation in Rh negative women.  78 Rh negative women who had amnios without receiving Rhogam were studied.  56 were at risk for sensitization.  3 (5.4%) were sensitized, but this was not significantly higher than the 2.1% rate of spontaneous Rh sensitization during pregnancy.  However, a trend towards increasing sensitization after amnio was noted.  Authors recommend use of Rhogam in Rh negative women undergoing amniocentesis.  

Amniocentesis and Fetal Damage

Bruce, S et al. Skin dimpling associated with midtrimester amniocentesis.  Pediatr Dermatol.  Oct. 1984. 2(2):140-2.  

"Multiple dimple-like scars occurred in an infant whose mother had undergone midtrimester amniocentesis."  The authors then discuss the prevalence and diagnosis of this situation.  Note that this is a case study, and that this probably occurred at a time when continuous ultrasound monitoring was likely not being done with amnios.  

Therkelsen, AJ and Rehder, H.  Intestinal atresia caused by second trimester amniocentesis.  Case report. Br J Obstet Gynaecol.  May 1981.  88(5):559-62.  

Horrifying case report, not for the squeamish.  This was from the days when continuous ultrasound was not used and would be unlikely to occur now, but is still a sobering reminder of the potential risks of amnios.  In a mid-trimester amnio, a string of fetal mucosa and submucosa from the fetus' small intestine was found.  The implication is that this was diagnosed as a possible abdominal defect.  The baby was aborted 21 days later.  "There was no lesion of the abdominal wall" but they did find probable signs of fetal damage from the amnio.  In other words, the needle probably hit the baby and perforated its abdomen, damaging it and putting intestinal mucosa into the amniotic fluid that was withdrawn.  The baby was aborted within 3 weeks, but no birth defect was found, only probable damage from the amnio.   

Cross, HE and Maumenee, AE.  Ocular trauma during amniocentesis. Arch Ophthalmol.  Oct 1973. 90(4):303-4.

No abstract is given with this case report, but there are a few case reports of eye damage to the fetus from amniocentesis.

Young, PE et al.  Fetal exsanguination and other vascular injuries from midtrimester genetic amniocentesis.  Am J Obstet Gynecol.  Sept. 1, 1977. 129(1):21-4.  

Case report of fetal exsanguination (the baby bled out and died) after a midtrimester amniocentesis.  Examined 242 consecutive amnios and the results suggested that "fetal hemorrhage is relatively common and difficult to avoid during this procedure."  Suggests that fetal hemorrhage may be more common when the placenta is anterior.

Epley, SL et al.  Fetal injury with midtrimester diagnostic amniocentesis.  Obstet Gynecol.  Jan 1979.  53(1):77-80.

Examined 107 infants born after midtrimester amniocentesis.  "The frequency of fetal injury was 9%, and was directly related to the number of attempts at amniocentesis.  All were minor cutaneous injuries except for 1 case of disruption of a patellar tendon." Made suggestions for reducing the incidence of "fetal puncture."  [Note that this study was done before continuous ultrasound was used during most amniocentesis procedures.]

Karp, LE and Hayden, PW.  Fetal puncture during midtrimester amniocentesis. Obstet Gynecol.  Jan 1977.  49(1):115-7.  

4 cases of fetal puncture during second trimester amniocentesis were reported in this study. In one cases, the baby "apparently sustained temporary neurologic damage."  The authors reviewed their own data and the research literature and concluded that fetal puncture occurs in 1-3% of midtrimester amniotic taps.  "We conclude that midtrimester amniocentesis should not be considered a routine benign procedure; and whenever the use of this diagnostic modality is being considered, the prospective parents should be informed of its hazards."  [Again, this study was done before continuous ultrasound was used with amnios.]

Strauss, A et al. Intra-uterine fetal demise caused by amniotic band syndrome after standard amniocentesis.  Fetal Diagn Ther.  Jan-Feb 2000.  15(1):4-7.

Presents a case report of Amniotic Band Syndrome associated with second-trimester amniocentesis.   Amniotic Band Syndrome occurs when the inner sac of waters is disrupted or ruptures and "strings" of the sac go through the amniotic fluid.  Sometimes these "strings" go across parts of the baby and cause scars, restricted growth of the part affected, or even amputation of fetal limbs.  In this case, the amniotic band restricted the umbilical cord and the fetus eventually died. Although most cases of Amniotic Band Syndrome are not associated with amniocentesis, a few cases may be, and the authors caution that invasive prenatal testing like amniocentesis can induce rare complications like Amniotic Band Syndrome.  

Kohn, G. The amniotic band syndrome: a possible complication of amniocentesis. Prenatal Diagnosis.  May 1987.  7(4):303-5.  

Another case report of fetal damage.  "Malformations of the upper distal extremeties were noted in an otherwise healthy infant whose mother underwent diagnostic amniocentesis.  A causal relationship is postulated."  

Rehder, H.  Fetal limb deformities due to amniotic constrictions (a possible consequence of preceding amniocentesis).  Pathol Res Pract.  July 1978.  162(3):316-26.  

Discusses the amniotic band syndrome and 2 case reports of this.  One is thought to be associated with a prior amniocentesis.

The Debate Over The Best Invasive Prenatal Test

Jauniaux, E et al.  What invasive procedure to use in early pregnancy?  Baillieres Best Pract Res Clin Obstet Gynaecol.  August 2000.  14(4):651-62.

Discusses the pros and cons of the various invasive prenatal tests available.  "Mid-trimester amniocentesis remains the safest invasive procedure.  Chorionic Villus Sampling (CVS) and early amniocentesis (EA) are associated with a higher risk of subsequent pregnancy loss.  There is also a 10-fold increase in the risk of mosaicism with CVS compared to amniocentesis.  Both CVS and EA can induce fatal structural defects and should be abandoned as routine invasive tests.  Patient counselling should include an evaluation of the risk associated with each individual procedure but also the operator's personal complication rate."

Alfirevic, Z et al. Chorion villus sampling versus amniocentesis for prenatal diagnosis. Cochrane Database Syst Rev.  2000 (2):CD000055.

Compared randomized trials of CVS to second trimester amniocentesis.  CVS was associated with more "sampling and technical failures, and more false positive and false negative results." Pregnancy loss was more common after CVS (odds ratio 1.33).  There was also a suggestion, not statistically significant, that there was an increase in stillbirths and neonatal deaths after CVS.  The authors concluded, "The increase in miscarriages after chrion villus sampling compared to amniocentesis appear to be procedure related.  Second trimester amniocentesis appears to be safer than chorion villus sampling.  The benefits of early diagnosis with chorion villus sampling must be set against the greater risk of pregnancy loss."

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