Copyright © 1998-2001 KMom@Vireday.Com. All rights reserved.
DISCLAIMER: The information on this website is not intended and should not be construed as medical advice. Consult your health provider. This particular web section on gestational diabetes is designed to present more than one view of a controversial subject, pro and con. It should be re-emphasized that nothing herein should be considered medical advice.
Who Is At Risk For GD
Who is most at risk for gestational diabetes? No one can predict with 100% accuracy who will get gd; according to some studies, nearly half the women who end up getting gd have no identifiable risk factors at all! Likewise, there are many women who have multiple risk factors for gd but never end up getting it anyhow. So you never know---it's difficult to predict. However, it can be helpful to know the characteristics that do tend to be associated with gd, so you can be extra-vigilant in your care. This is only sensible, since gd (especially if it shows up early or severely) can cause definite risks to the baby.
If you are not yet pregnant, you should plan on having your blood glucose tested BEFORE trying to conceive, so that you can clearly establish that your blood sugar is normal beforehand. If it is not, it is vitally important to get it under control before trying to get pregnant; high blood sugar at conception and in the first trimester is strongly associated with multiple birth defects and miscarriage/stillbirth. The best test to get is the glycosylated hemoglobin (abbreviated as HbA1c), which is more conclusive. It measures your average blood sugar over the space of about 2 months or so, and gives a clearer picture of your bG status. Another test that is often used instead because it is cheaper and easier is the fasting blood glucose test. This involves an overnight fast and a blood draw. Its weakness is that it is simply a one-time snapshot of your bG levels on THAT day, and it is easy to get either higher or lower numbers than normal due to other circumstances such as stress, illness, amount of time since eating, etc. It also reflects only fasting numbers; there are some women with type II diabetes who have normal fasting numbers but abnormal responses to food intake. Either fasting or post-meal abnormalities in blood sugar are a risk to baby, so it's best to be sure ALL is normal.
If possible, Kmom recommends using the HbA1c test, since it represents a truer overall and long-term picture, but the fasting test may be used by some providers anyhow. Either way, ask for your test results and the diagnostic levels used, and be sure to keep a record of these for yourself, even if all is well. If your blood sugar is normal and all other factors are fine too, then you can go ahead with your plans to conceive, knowing that you are giving your child the best possible start. It is still wise, even if normal, to begin a gd food plan before becoming pregnant, as this may help prevent some cases from developing during pregnancy, or at least keep them from being more severe in other cases. A plan for regular daily exercise is also important. Since gd does occur more often in larger women, it is best to be very proactive about preventing/treating it. (See the websections on GD: Nutrition Questions and GD: Can It Be Prevented?.)
If you are already pregnant, it may be appropriate to have your blood sugar tested in both the first and second trimester. Normally, most women have their blood sugar tested between 24-28 weeks, when the placental hormones become strong enough to interfere with insulin sensitivity. However, women with very strong risk factors (and obesity is a risk factor, though certainly not a causal connection) should probably be tested earlier in the pregnancy as well. Catching a more severe case of early-onset gd can help prevent a lot of problems later on for baby; it is to your great advantage to discover gd early, if it exists.
Your doctor should not be testing you for gd every month simply because of your size, but once in the first trimester and once in the second trimester may be sensible if you have multiple risk factors (especially a strong family history of diabetes or a diagnosis of PCOS). If your results are borderline in any way or there are other medical indications, then a test in between or again at 32 weeks might be appropriate in a few cases, but is usually not necessary for most women.
If you feel that your provider is deluging you with unnecessary testing or feels that you WILL get gd simply because of your size, you should strongly consider switching providers. The vast majority of large women do NOT get gd, and a doctor's attitude that you are high-risk disaster just waiting to happen is extremely harmful. You need a size-friendly provider instead, one that will recognize the risk factors and test appropriately for them, but who will not assign added intervention, over-monitoring, or negativity where there is no proven need. This is very important! (See the websection on Finding a Size-Friendly Provider.)
The Risk Factors
Risk factors for gestational diabetes vary from study to study, but some remain consistent. These are listed as 'strong' associations solely due to their consistency of appearance in each study, and are put near the top. Others whose associations are less clear are listed towards the bottom. Remember that research varies and is sometimes contradictory. Some of these could be disproved at a later time.
It is also very important to remember that these risks are theoretical and it may be possible to mitigate their effect by being proactive; also remember that many women with multiple risk factors never do, in fact, develop gd. If you find you have multiple risk factors for gd, take it simply as a need to test more carefully and be extremely proactive in your diet and exercise for the pregnancy, not as a sentence of doom. Kmom cannot emphasize the need for proactive health measures from the start often enough! Don't be passive; actively try to reduce your risks through excellent diet and daily exercise and great prenatal care from a non-sizist provider. This is very important!
1. A family history of diabetes is very strongly associated with gd, especially when a first-degree relative had diabetes. If your parents or a sibling has diabetes, you will want to be extremely proactive about trying to prevention and testing. A mother who had gd in her pregnancy with you may be especially predictive of problems, according to some sources.
2. Age is a very strong risk factor too. Women under 25 rarely get it, though it does happen occasionally. The rate begins to increase over age 25, but particularly over 30. Some studies show an even greater rate over 35. Still, 'advanced maternal age' does not have to mean gd!
3. Parity (number of kids, especially 3-4 or more) is also strongly associated with gd in some studies. This factor seems to be independent of the increasing weight and age that usually accompany increasing parity. It's important to remember that just because you did not have gd in previous pregnancies does not mean that you will not get it in a future pregnancy. However, just because you are having your fourth child doesn't mean you will get it, either.
4. A previous pregnancy with gd is very strongly associated with recurrence. Chances are generally cited as 2 of 3, with it often recurring earlier and more severely, although some studies show the rate of recurrence as lower. It should be noted that it does not always recur----Kmom had a mild case of gd in her first pregnancy but avoided its recurrence in subsequent pregnancies by being very proactive. (Remember that if 2 of 3 recur, then 1 of 3 will not.) Still, once you have had gd, you are always at higher risk of it recurring in any future pregnancy, even if you avoided it at another time. Always act proactively if you have a history of gd.
5. Obesity, usually measured by Body Mass Index (BMI), is strongly associated with gd. It is unclear whether gd incidence goes up as BMI/weight goes up, although some evidence does seem to point this way. However, obesity does not CAUSE gd. In fact, the vast majority of obese women (even of very large size) do not get gd, yet many average-sized women do. There is NOT a causal relationship, but obesity certainly is a risk factor. Studies do not, of course, attempt to separate the effects of weight itself independent of yo-yo dieting, sedentary lifestyles, genetics, or high fat/high refined carbohydrate diet. Perhaps gd is a combination of genetic predisposition and environmental, dietary, exercise and metabolic factors, but we won't know for sure until more discerning testing criteria are used.
6. A previous child over 4000g (almost 9 lbs) indicates a fairly strong risk of gd in subsequent pregnancies, although macrosomia can also be due to genetic size inheritance as well as maternal hyperglycemia/fetal hyperinsulinemia.
7. Women whose own birth weights were over 9 lbs. have a fairly strong risk of gd. Again, this can be genetic inheritance or maternal hyperglycemia/fetal hyperinsulinemia or both. If your 'mother had gd with you, then your chances are strongly increased. However, since gd was not routinely tested for then (and the tests then did not use the same strict standards as now), many women who probably had 'gd' went undetected. A birth weight over 9 lbs. may indicate that your mother had gd, or it could just be genetic inheritance.
8. Unexplained multiple miscarriages, stillbirths, or birth defects (so-called 'poor obstetric history') may be due to undiscovered gd/diabetes in some cases (but certainly not all). Women who have multiple loss history tend to have increased rates of gd. However, there are many causes of miscarriage and other problems; do not assume that undetected gd is to blame without further evidence. It's just one more thing to check into.
9. Non-white ethnicity is associated with gd, although studies vary a bit. More studies need to be reviewed, but it seems to be consistent that people who emigrate to other countries tend to have slightly higher rates than the same ethnic population in their home country. It's also important to note that most of the world uses the World Health Organization's gd criteria, which is less stringent than the National Diabetes Data Group criteria, and so some of their populations may be underdiagnosed by US standards (or US rates may be overdiagnosed).
10. Weight gain in early adulthood is associated with higher rates of gd in some studies. In other studies, it is weight gain between pregnancies that is a risk factor. Weight gain during pregnancy has been found to be a factor in some studies but not others and is generally not thought to be that significant a factor, but it depends on the source read. Some studies found that women who gained 'too much' during pregnancy were at risk, but they also found that some women who 'gained too little' were also at risk. Large women with weight gains around 15 pounds were found to be less at-risk than those above or below; however, this was not conclusive and needs more study. Furthermore, artificially trying to achieve a weight gain of 15 pounds by either strongly restricting calories or adding extra food or fat levels may cause far more problems than it solves. It is best to aim instead for eating well and reasonably and not focusing on weight gain unless it is excessive. Many larger women just do not gain weight in pregnancy no matter what they do; this need not be an area of extreme concern as long as nutrition is excellent.
11. "Central fat distribution" is another predictive factor for gd. In some studies, 'apples' (women with larger waists or larger waist/hip ratios) were found to have an increased risk of gd. Every degree of increase in waist size or waist/hip ratio seemed to increase risk.
12. PCOS (PolysCystic Ovarian Syndrome) is definitely associated with higher risks of gd. (This is put near the bottom of the risk list only because it is taken from PCOS studies, not gd studies, which do not generally look at PCOS issues). One common marker of PCOS is insulin resistance, so it is logical that this might be increased even more under the influence of pregnancy hormones. Several studies found higher rates of gd and Impaired Glucose Tolerance among PCOS women, especially if the women were hyperinsulinemic prior to pregnancy. PCOS is also associated with higher rates of Pregnancy-Induced Hypertension (pre-eclampsia) and there is evidence that this also may be due to hyperinsulinism. Women with PCOS should be extremely proactive about healthy habits and food intake during pregnancy, and early monitoring is probably a good idea as well.
13. Cigarette smoking is also associated with higher rates of gd in several studies. Considering the many other risks in pregnancy that smoking is associated with, women should absolutely quit smoking when pregnant.
14. Multiple Pregnancies often have an increased occurrence of problems like gd and pre-eclampsia. The effect of twice the hormones may overload the insulin sensitivity of moms who might otherwise not develop gd in singleton pregnancies. Moms with twins or more should be monitored earlier and possibly more frequently. Some studies have found that dizygotic (fraternal) twin pregnancies were more likely to have gd than monozygotic (identical) twin pregnancies, probably due to the number of placentas (producing twice the hormones to interfere with insulin usage).
15. History of Skin/Urinary Tract/Genital Infections is also associated with higher rates of gd. High blood sugar levels often lead to yeast infections of the skin or vagina, and can also increase the number of bacterial UTIs. Frequent recurring/hard-to-cure infections like this, both previous to or during pregnancy, may be markers for gd.
16. Hypertension is listed by one source as being associated with gd, though this seems to be true more often in reverse (women with gd often get Pregnancy-Induced Hypertension, whereas most women with PIH don't necessarily get gd). The underlying connection here is probably strong insulin resistance, since this is thought to create blood pressure problems as well as diabetes problems.
17. Chronic Steroid Use may also be associated with higher rates of gd, though this connection is not often mentioned. If you have used steroids such as prednisone chronically for medical conditions or whatever, you will want to carefully monitor your bG levels before and throughout pregnancy. Glucocorticoids (such as prednisone and others) often decrease glucose tolerance markedly. Be sure to consult your provider carefully about these and other medications (such as terbutaline, progesterone, etc.) which can decrease glucose tolerance as well.
18. Polyhydramnios (excessive amniotic fluid) is sometimes associated with gd pregnancies. If you had a pregnancy complicated by polyhydramnios, you will want to be monitored a bit more closely for gd, just in case. If you have gd, they will watch carefully to monitor the level of amniotic fluid present during your pregnancy.
Translating the Risks into Numbers
Many women will want to know exactly how much increased risk they have due to various risk factors and how this compares to gd rates in the overall population. It is difficult to quantify this, since studies vary so strongly at times and so many factors are involved. Kmom is very hesitant to publish specific figures, but felt that she would want to know if she were just beginning to research this field.
So, with many caveats and cautions, here are some of the specific figures she has run across in reviewing a number of gd studies. Remember that some studies could be high or low, depending on the screening used, the adjustment for various confounding factors, the methodology of the researchers, the iatrogenic influence of the doctors involved (doctor-caused problems), and the various diagnostic thresholds used, etc. More studies also need to be reviewed to see if these studies stay consistent with the figures already found. Remember also that one issue that is rarely addressed is whether these rates could be lowered through proactive measures early in pregnancy or before pregnancy.
Kmom chose to express most of these risks in terms of the percentage of the population that developed only gd (not Impaired Glucose Intolerance, a subset slightly below the levels of gd, since the data on the risks of IGT is less clear). She mostly chose not to include relative risk ratios, since these are not as meaningful as the percentage of a group that had gd. For example, in neural tube defects, some studies have found that larger women have a risk 2-4x greater of babies with neural tube defects, and this is how the press reported the study, making large women everywhere panic. (Four times the risk!) A closer look at the percentages, however, reveal that even with the supposed increase in risk, less than 1% of large women actually have babies with such problems. It is still statistically significant and should not be overlooked, but it is important not to exaggerate and scare women either. Risk ratios can be useful in some ways, but are less meaningful out of context, so Kmom chose not to use these for most cases.
Also, remember that more data is needed. As Kmom finds more reports that quantify these issues, she will update this section, so be sure to check back periodically if you wish.
GD rates in:
Total overall USA population - usually quoted at about 3-4% for the overall nation in books; will vary based on the ethnicity of the population involved and the diagnostic criteria used. Actual reports vary from 1-14%, with the highest numbers being reported in Los Angeles and Zuni, New Mexico, two areas with strong concentrations of high-risk populations.
Obese Women (Body Mass Index > 30) - from 12-20%, depending on the study examined. In other studies the risk was 2-3x that of average-sized women when corrected for other confounding factors. Women with BMIs over 30 had an occurrence of 12% in one study; another study that looked at the rates only for women over 300 lbs. found a rate of 20%. This may indicate that risk increases with size, but more information is needed, and the effects of dieting, etc. need to be looked at as well. But certainly, for whatever reason, larger women do have somewhat higher rates of gd. However, it's also important to note that even in the highest risk group, women over 300 lbs., eighty percent still did not get gd! So being large does not make gd a foregone conclusion at all, only something that should be carefully screened for.
Age > 30 - About 8-9%; probably goes even higher for women over 35.
Family History of Diabetes - About 11-12%; may be higher for those with first-degree family members with diabetes (parents, siblings). It is difficult to separate the role of obesity and family history in diabetes, since most type II diabetics are heavier. But it's clear that family history of diabetes is probably a VERY strong risk factor.
PolyCystic Ovarian Syndrome - These studies varied a lot, probably due to the very small sample sizes used. Rates varied between 12-25%, and it's important to note that PCO risk was independent of Body Mass Index risk in at least one study (thin PCO patients got gd just as much as larger PCO patients). PCO patients with hyperinsulinemia before pregnancy was strongly predictive in one study (>80%), though the sample was extremely small and easily skewed, so beware placing too much credence in it.
- Chinese - 0.6% to 7% for those living in China, on average; 4-15% in immigrant populations in Australia or Singapore
- Southeast Asian (Vietnamese, etc.) - 10% or more, as an immigrant population (larger 7x risk in another study)
- Korean - extremely low rates within Korea, about 1-2%; unknown in immigrant populations
A paper from the Fourth International
Workshop-Conference on GDM found that the frequency
of GD in various ethnic groups varied from 1.6% in non-Hispanic white women in
California, 1.7% in black/African women in California, 4.2% in Hispanic women in
California, 1.2% in white women in London, 2.7% in black women in London, 5.7%
in Jewish women in Israel, 6.0% in Mexican women overall, and 14.3% in Zuni
Indian women. As noted, immigrant
populations who migrate to Western countries seem to be at highest risk; Chinese
women in Taiwan had a 0.6% rate of GD, whereas women of Chinese ancestry in
California had a GD rate of 7.3%. Overall,
the USA has a rate of about 4.0% of GD in all ethnic groups combined.
Bobrowski, R.A. and S.F. Bottoms. Underappreciated Risks of the Elderly Multipara. American Journal of Obstetrics and Gynecology. 172(6):1764-7; discussion 1767-70, June 1995.
Looks at the risks of the older mother who has already had children. Notes that more emphasis has been placed in the past on the older mom who is having children for the first time, and that the risks of the older mom with previous pregnancies is underappreciated. Found 2x the risk for induction, 3x the risk for pre-eclampsia, 4.5x the risk for gd, 3x the risk for clinical diabetes, 2x the risk for use of oxytocin, and 1.6x the risk for macrosomia. Especially notes that the risk for pre-eclampsia was higher than expected.
Engelgau, M.M. et al. The Epidemiology of Diabetes and Pregnancy in the U.S., 1988. Diabetes Care. 18(7):1029-33, July 1995.
Looked at a representative sample of the U.S. population to determine the prevalence of pregnancy complicated by diabetes. Found that it affected 4% of all pregnancies in 1988, 88% of which were gd pregnancies, 8% type II pregnancies, and 4% type I pregnancies. "In multivariate analyses, the odds of having a pregnancy complicated by GDM increased significantly with maternal age and body mass index...More frequent testing may further increase the apparent prevalence of GDM."
Hoskins, R.E. Zygosity as a Risk Factor for Complications and Outcomes of Twin Pregnancy. Acta Geneticae Medicae et Gemellololgiae. 44(1):11-23, 1995.
Retrospective study from all recorded live twin births in Washington State in 1984-88 in order to determine the risk of zygosity (fraternal vs. identical twins) on pregnancy complications and birth outcomes. Found that identical twins were more likely to have shorter gestations and low birthweight, as well as other adverse newborn conditions. Fraternal twin pregnancies were more likely to have gestational diabetes occur, probably due to the presence of two placentas "which may support greater insulin antagonism" than the single placenta of the mother of identical twins. The estimated risk for gd in fraternal twin pregnancies vs. in identical twin pregnancies was about 8.6.
Fujimoto, W.Y. et al. Susceptibility to Development of Central Adiposity among Populations. Obesity Research. 3 Suppl 2:179S-186S, September 1995.
"There is good evidence that central (visceral) adiposity is important in the development of the insulin resistance or metabolic syndrome...[also known as Syndrome X]...It is proposed that some non-Caucasian populations are especially susceptible to development of this syndrome, and that lifestyle changes may play important etiologic roles."
Jang, H.C. et al. Screening for Gestational Diabetes Mellitus in Korea. International Journal of Gynaecology & Obstetrics. 51(2):115-22. November 1995.
The prevalence of GDM in Korean women was 2.2/100. Although the incidence of obese women is low in Korea, the prevalence of GDM significantly increases with increasing body mass index. Suggests that universal screening using 135 mg/dl as a threshold and early screening of those with 2 or more risk factors 'represents the most effective paradigm for Korea'.
Branchtein, L. et al. Waist Circumference and Waist-to-Hip Ratio are Related to Gestational Glucose Tolerance. Diabetes Care. 20(4):509-11. April 1997.
Study involving 1000+ Brazillian women. "Central fat distribution measured in pregnancy is an independent predictor of gestational glucose tolerance...glycemic level was .11 and .13 mmol/l greater for each standard deviation increase in WHR (.06) and waist circumference (8.0 cm), respectively....this finding supports the concept that NIDDM and gestational diabetes are parts of the same disease, differing basically in their moment of detection."
Moses, R. et al. Gestational Diabetes: Do All Women Need to be Tested? Australian & New Zealand Journal of Obstetrics & Gynaecology. 35(4):387-9. November 1995.
Tested 1,185 women. Compared the number of cases of gd in women without risk factors vs. those with risk factors----1/3 of cases would have been missed had screening been based on risk factors alone. In this study, a total of 6.7% total women had gd. 8.5% of women over 30 had gd, 12% of women with a Body Mass Index over 30 had gd, 11.6% of women with family history of diabetes in a first-degree relative had gd. 5% of women without any risk factors had gd.
Solomon, C.G. et al. A Prospective Study of Pregravid Determinants of Gestational Diabetes Mellitus. Journal of the American Medical Association. 278(13):1078-83. October 1, 1997.
Used the Nurses' Health Study II to assess whether recognized determinants of NIDDM may also be markers for increased risk of GDM. Analyzed 14,613 women between 1990-94 with singleton pregnancies with no previous gd or diabetes. 4.9% reported gd. "Advanced maternal age, family history of diabetes mellitus, nonwhite ethnicity, higher BMI, weight gain in early adulthood, and cigarette smoking predict increased GDM risk."
Dornhorst, A. et al. High Prevalence of Gestational Diabetes in Women from Ethnic Minority Groups. Diabetic Medicine. 9(9):820-825. November 1992.
11,205 women from a multiracial antenatal clinic in London were assessed for the influence of ethnic origin, body mass index, and parity (# of kids) on gd. "Ethnic origin was the dominant influence on the prevalence of gestational diabetes." Black women had 3x the risk compared to white British women, SE Asian women had 7x the risk, Indian women had 11x the risk. Increasing age was an independent risk factor in all but SE Asian women. Obesity was a risk factor in all ethnic groups except Indian and SE Asian women. Parity > or = 3 was an increased risk for gd in only White, Black, and SE Asian women.
Ray, R. et al. Gestational Diabetes in Singaporean Women: Use of the Glucose Challenge Test as a Screening Test and Identification of High Risk Factors. Annals of the Academy of Medicine, Singapore. 25(4):504-8. July 1996.
4.2% of Singapore women studied had gd; 140 mg/dl was found to be a better screening cutoff than 130 mg/dl. Risk factors for gd in the study included age >30 years, obesity, Chinese ethnicity, and by some analyses, parity of 4 or more pregnancies.
Yue, D.K. et al. Why Does Ethnicity Affect Prevalence of Gestational Diabetes? The Underwater Volcano Theory. Diabetic Medicine. 13(8):748-52. August 1996.
"To study why gestational diabetes (GDM) is more common in some ethnic groups than others, we tested the hypothesis that GDM is more common in people who are temporally closer to developing non-insulin-dpendent (Type 2) diabetes mellitus (NIDDM)...For women of different ethnic origins there is a difference in the time gap between their pregnancies and the time at which they would on average be expected to develop diabetes. This difference may be an important factor underlying the higher prevalence of GDM in some ethnic populations." The overall presence of gd was 6.7%. In Anglo-Celtic women it was 3%, in Chinese women it was 15%, Vietnamese - 9.6%, Indian - 16.7%, Arabic - 7.3%, and Aborigines - 10.1%. The study sample included 6,052 patients.
Lee, C.P. et al. A Multicentre Study to Investigate the Prevalence of Abnormal Carbohydrate Metabolism in Chinese Pregnant Women. Journal of Obstetrics and Gynaecology Research. 22(4):401-7. August 1996.
Study of 713 pregnant women in China (not emigrants). The prevalence was 6.9% overall. Heavier women had more abnormal glucose intolerance. The birth weight ratio of the babies was positively correlated with maternal height and to a lesser extent, fasting serum glucose but not with the 2 hour serum glucose.
Meza, E. et al. Gestational Diabetes in a Mexican-U.S. Border Population: Prevalence and Epidemiology. Revista de Investigacion Clinica. 47(6):433-8. Nov-Dec. 1995.
519 women in Juarez, Mexico were studied. 11% had gd, and a further 9.4% had at least one abnormal value on the GTT. Patients with gd tended to be older, had more kids, lower height, higher weight, and more family history of diabetes.
Lopez-de la Pena, X.A. et al. Prevalence of Gestational Diabetes in a Group of Women Receiving Treatment at the Mexican Institute of Social Security in Aguascalientes, Mexico. Archives of Medical Research. 28(2):281-4. Summer 1997.
187 pregnant women were studied in one year; 6.9% developed gd. They found significant differences among parity, fasting blood glucose, macrosomia, family history of diabetes, obesity of 200 lbs. or more, and age>35 years.
Proceedings of the Fourth International
Workshop-Conference on Gestational Diabetes Mellitus. Diabetes Care. August
1998. Volume 21 (Supplement 2), text available at the following website, http://www.diabetes.org/DiabetesCare/Supplement298/B161.htm.
Studies used include:
King, H. Epidemiology
of Glucose Intolerance and Gestational Diabetes in Women of Childbearing Age.
Screening for Gestational Diabetes Mellitus.
Copyright © 1998-2001 KMom@Vireday.Com. All rights reserved. No portion of this work may be reproduced, reprinted, or sold, either by itself or as part of a larger work, without the express written permission of the author; this restriction covers all publication media, electrical, chemical, mechanical or other such as may arise over time.
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