Gestational diabetes: What it is, what to do about it

In some women—especially those who are overweight—the body can be resistant to the effects of insulin and blood sugars run high even though a normal or even greater-than- normal amount of insulin is produced. This is true with many cases of adult-onset diabetes.

Obstetricians have long known that pregnancy is a state of insulin resistance. Hormones produced by the placenta, including human placental lactogen, counteract the effects of insulin so more insulin is needed to maintain blood sugars at their usual levels. Some women (and their pancreases) cannot produce the needed extra insulin and their blood sugars run high during pregnancy. This condition is known as gestational diabetes (GDM) and is usually not manifest until the third trimester of pregnancy.

GDM, while not as concerning as diabetes that is present before conception, is associated with risks of having larger babies (fetal macrosomia), needing cesarean delivery (in part because of larger babies), and, paradoxically, babies' requiring treatment for low blood sugars after birth. Because some evidence suggests that outcomes are improved if diabetes is treated during pregnancy, most pregnant women are screened for GDM early in their third trimester. Screening involves measuring blood glucoses levels after women have been given one or a series of sugar drinks.

About 5% of pregnant women will be diagnosed with GDM, and diagnosis is more likely in women who are older, heavier, or who are pregnant with twins. Once diagnosed, patients are asked to modify their diets, plan regular exercise (walking will do) and monitor their blood sugars with a small device that can be used at home.

If blood sugar levels remain high in spite of diet and exercise, medication may be recommended. Many women begin treatment with a pill (glyburide), but sometimes injections with insulin may be needed. When sugars are high or medication is needed,  a woman may have extra ultrasounds or other tests to make sure that the pregnancy remains as healthy as possible.

Blood sugar values almost always return to normal after delivery, but women who have had a pregnancy complicated by gestational diabetes are at risk for developing adult onset diabetes (insulin resistance again) later in life. Women who have had GDM should have blood sugar testing 6-12 weeks after delivery and again at intervals  of 1-3 years.  If you have had GDM, tell your primary care provider. In addition to testing, he or she may recommend a continued program of diet and exercise to minimize the risk for developing diabetes outside of pregnancy.

Jeffrey Ecker, M.D., is an attending perinatologist (high-risk obstetrician) at Massachusetts General Hospital. He is also an Associate Professor at Harvard Medical School.

Diabetes

Nearly 21 million Americans suffer from diabetes, and as anyone who has been affected by the disorder knows, it is about much more than a statistic: it means a new way of life. Diabetes: A plan for livingis a special report from Harvard Medical School that will help you learn how to better understand and manage your diabetes, including type 1 and type 2, as well as other variations of the disease. This report will show you that it's not just possible to live with diabetes; it's possible to live well.

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