Treatment of Gestational Diabetes Beneficial Even in Mild Cases

It’s not well understood why some women who have never shown signs or symptoms of diabetes develop the condition during pregnancy, but it is clear that left untreated, gestational diabetes poses risks for both mother and child. Mothers have an increased chance of high blood pressure during pregnancy, greater likelihood of having an oversized baby and the need for a cesarean section delivery, and stillbirth. Children born to women with gestational diabetes face not only delivery complications but an increased risk for childhood and adult obesity and an increased risk of developing type 2 diabetes later in life. Diagnoses and treatment of gestational diabetes is key to minimizing these complications and improving pregnancy outcomes, and recent studies show that is true even for women with the mildest form of the condition.

The study, conducted by researchers in the Maternal Fetal Medicine Units Network of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human (NICHD), included 958 women who were between 24 and 31 weeks pregnant who had mild gestational diabetes, defined as normal blood sugar levels after fasting but abnormally high levels in at least two readings over the course of three hours after an oral glucose tolerance test. The women were randomly assigned to receive either diabetes treatment consisting of dietary counseling, instructions on how to monitor their glucose and insulin if necessary, or standard pregnancy care.

Compared to their untreated counterparts, the women who received diabetes treatment were 60 percent as likely to develop high blood pressure during pregnancy or to develop preeclampsia, a life-threatening complication that can lead to maternal seizures and death, and 80 percent as likely to give birth by cesarean section. Babies born to the women in the treated group were half as likely to be overweight or abnormally large and to experience shoulder dystocia, a condition where the baby’s shoulder becomes lodged inside the mother’s body during delivery. “Whether to treat mild gestational diabetes has never been entirely clear,” said coauthor Catherine Y. Spong, chief of the Pregnancy and Perinatology Branch at the NICHD. “The study results show conclusively that both mothers and infants do better when gestational diabetes is controlled.”

In an editorial accompanying the study in The New England Journal of Medicine, Dr. David Sacks, a maternal-fetal medicine specialist at the Kaiser Foundation Hospital in Bellflower, California, said the results of the study combined with a 2005 Australian study that also found treating gestational diabetes reduced the rate of serious complications around the time of delivery “clearly support the treatment of gestational diabetes” but posed the question, “however, now that the value of treatment is established, whom do we treat?”

Boyd Metzger, professor of metabolism and nutrition at the Northwestern University Feinberg School of Medicine, suggests the answer to that question may be found when new international guidelines for diagnosing gestational diabetes are published. Metzger was the lead scientist for the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study, a six-year study that spanned nine countries and included about 25,000 women. HAPO found a continuous increase in complications as blood sugar levels rose, indicating that treatment would be beneficial at any point.

Dr. Miriam Greene, an obstetrician and gynecologist at NYU Langone Medical Center, says she has already been treating women with the mildest forms of gestational diabetes, and that it does make a difference. Clearly, “when women with mild gestational diabetes are treated well, there’s a decreased incidence of birth trauma,” she said. 

Rates of gestational diabetes have been increasing as more women begin their pregnancy overweight. The condition affects from 1 to 14 percent of all U.S. pregnancies and is thought to occur because of hormone changes that interfere with the body’s ability to make and use all the insulin it needs, causing blood glucose levels to get too high. The good news is that gestational diabetes usually goes away after the baby is born. The bad news is that women who develop the condition may also get it again in subsequent pregnancies.