Gestational diabetes mellitus (GDM), or high blood sugar during pregnancy, used to be relatively rare, occurring in about 3 percent to 4 percent of pregnancies. But in recent years, the rate has doubled—now, up to 6 percent to 8 percent of moms-to-be are diagnosed with this prenatal complication. And new recommendations lowering the cutoff point for diagnosis may lead to an even more dramatic increase. If these new guidelines from an international panel of 50 experts are adopted in the United States, 16 percent of pregnant women may hear the words, “You have gestational diabetes.”
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In women with GDM, excess glucose (blood sugar) passes from the mother’s bloodstream through the placenta. Serious pregnancy complications include preeclampsia (a serious high blood pressure condition that can be fatal), preterm delivery and delivery of overweight babies, often via Cesarean section. Some 70 percent to 80 percent of women diagnosed with GDM in the United States eventually develop type II diabetes.
New research is showing that GDM can have long-term consequences for children as well. “Children of women with GDM are at risk for developing type II diabetes themselves,” says Danielle Downs, Ph.D., an associate professor of kinesiology and obstetrics and gynecology at Pennsylvania State University who conducts research on gestational diabetes. But even normal-size babies who are born to mothers with untreated GDM are at greater risk of becoming overweight kindergarteners—and, consequently, overweight adults.
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Although being overweight is a major risk factor for GDM, only about half of women diagnosed with it carry excess pounds. Age is also a factor—women age 25 and older, but especially older than 35, are at greater risk—and genes play a role: You can be healthy and lean and still develop GDM because of a genetic predisposition or other factors.
Lowering the threshold. Currently, women in the United States routinely undergo a GDM screening between 24 weeks and 28 weeks of pregnancy. At your doctor’s office, you drink a bottle of super-sweet soda—think Mountain Dew spiked with pancake syrup—and an hour later, your blood is drawn.
If your blood sugar is higher than 140 milligrams of glucose per deciliter of blood plasma (mg/dL), you are referred to a laboratory for an oral glucose tolerance test (OGTT). This one involves an overnight fast, then drinking a soda that’s monumentally sweeter than the first one and having blood drawn four times over three hours. If your blood sugar exceeds a designated threshold at two of the four blood draws, you are diagnosed with GDM.
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This process will change significantly if the international panel’s recommendations, under consideration by the American Diabetes Association and The American College of Obstetricians and Gynecologists, are adopted in the U.S., as they have been in Japan. The doctor’s office screening will be dropped, and all pregnant women will undergo a two-hour, three-blood-draw version of the OGTT, including the overnight fast but requiring a smaller amount of glucose-sweetened beverage. If the results of just one of the three blood draws exceed a threshold that is slightly lower than the current numbers, GDM will be diagnosed.
Why the proposed change? Because new studies show that blood sugar levels previously considered healthy actually are associated with higher rates of pregnancy complications. Women considered to have GDM under the proposed lower cutoff—many of whom are not included with the current guidelines—have double the risk of delivering an overweight baby and developing preeclampsia and a 45 percent greater chance of delivering early or having a C-section. “These are really substantial differences,” says Boyd E. Metzger, M.D., chairman of the panel and an endocrinology professor at Northwestern University Feinberg School of Medicine in Chicago.
Out with the old. Metzger and his panel believe that it’s time to replace the current guidelines, since they were adopted 40 years ago, when the primary consequence of GDM was thought to be a risk to the mother of developing type II diabetes later in life. “It wasn’t known that gestational diabetes carries risk to the pregnancy,” Metzger notes.
Here’s the good news: Though some women require insulin injections, most GDM cases can be treated through regular exercise and dietary changes, such as eating fewer sweets and smaller, more frequent meals. “It’s very likely that treatment will be effective,” Metzger says.
If you’re diagnosed with gestational diabetes, under the current guidelines or the proposed new ones, know that the lifestyle changes you will be asked to make during pregnancy and postpartum and thereafter will help keep you healthy for years to come. “For many women,” says Downs, “a diagnosis could be the best thing that ever happens to them.”
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Who's most at risk?
Some of the latest research findings about gestational diabetes:
- Women who gain excess weight in the first trimester are at higher risk, according to a 2010 study published in Obstetrics and Gynecology. The association was even stronger among women who started their pregnancies overweight, a study at Kaiser Permanente Medical Group in Oakland, Calif., found.
- Korean-American and Filipino-American women have twice the risk of GDM compared with Caucasian and African-American women, another recent Kaiser Permanente study found.
- Women who drink five or more sugar-sweetened sodas a week before conceiving have a higher GDM risk, according to a study conducted by Harvard University and Louisiana State University.
- Women with gum disease have higher odds of developing GDM than women with healthy gums, a New York University study found.
- Frequent snorers have a 14.3 percent chance of developing GDM, compared with a 3.3 percent chance for women who don’t snore, according to a Northwestern University study.
