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Reviewed By Louise Chang, MD
Sept. 30, 2009 -- Treating pregnant women who have even mild gestational diabetes helps reduce the risk of complications in infants and the women's own risk of blood pressure problems, according to a new study.
While gestational diabetes -- defined as having glucose intolerance that first shows up during a pregnancy -- has long been known to increase the risk of the woman getting diabetes later in life, the risk of ill effects on the pregnancy has not been as clear. Those women whose blood sugar levels are very elevated appear to be at risk of complications, but how the milder form of gestational diabetes affects the pregnancy has not been known exactly, the researchers say.
The new study finding "provides the evidence to endorse screening and treating women even with mild gestational diabetes," says Catherine Spong, MD, chief of the pregnancy and perinatology branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health, and a co-author of the study. It is published in the New England Journal of Medicine.
Up to 14% of U.S. pregnancies are affected by gestational diabetes, according to the researchers.
In the study, Spong and colleagues, with lead investigator Mark Landon of The Ohio State University Medical Center, Columbus, randomly assigned 485 pregnant women with mild gestational diabetes to the treatment group and 473 to the comparison group. The women were cared for at 15 different medical centers.
To qualify for the study, women were in the 24th to 31st week of pregnancy and had a diagnosis of mild gestational diabetes. For the study, researchers defined mild gestational diabetes as having a fasting glucose level of less than 95 milligrams per deciliter and having at least two of three timed glucose measurements taken one hour, two hours, and three hours after drinking a sugary beverage that exceeded established thresholds.
Gestational diabetes is believed to occur in some women after increased levels of some hormones that rise during pregnancy hamper the ability of insulin to manage blood sugar. When blood sugar levels rise too much, it can adversely affect the baby, causing it to grow too big, among other potential problems.
The comparison group received usual prenatal care; two women in that group needed insulin to control blood sugar levels.
Women in the treatment group were advised to exercise and received nutritional counseling, learning how to spread their carbohydrate consumption throughout the day to better regulate blood sugar levels, Spong tells WebMD. They then monitored their blood glucose levels at home to be sure the diet therapy helped keep blood sugar within the desired target range. Of the treatment group, 93% managed with diet alone, while 7% needed insulin injections to control their blood sugar.
The researchers then compared the outcomes of the two groups.
Advantages of Treatment of Gestational Diabetes
Women in the treatment group had a number of advantages, the researchers found. "If treated, they were half as likely to have a large baby," Spong says. Large babies are at risk for health problems later in life, including obesity.
Those in the treatment group also were:
- Less likely to need cesarean delivery. While 26.9% of the treatment group had C-sections, 33.8% of the comparison group did.
- Less likely to deliver babies with shoulder dystocia, in which the shoulder gets "stuck" during delivery and it becomes an obstetrical emergency. Bigger babies are at higher risk.
- Less likely to have pregnancy-related high blood pressure and preeclampsia.
Neither group experienced stillbirths or newborn deaths, another area the researchers wanted to compare.
Until this study, Spong says, "it hadn't been known if treating those with mild gestational diabetes improves pregnancy outcome." Now, she says, the study provides evidence supporting screening and treating women even with mild gestational diabetes.
"The treatment is pretty straightforward -- it's diet and exercise," she says. But that's not to say it's simple, she acknowledges, especially if a woman already has young children to care for. The exact diet and exercise instructions in the study were left up to the doctors, she says. Typically advised are carb counting and taking a brisk walk after a meal to help regulate blood sugar levels, Spong says.
The message for pregnant women from the study is clear, says Eva Pressman, MD, professor of obstetrics and gynecology and director of the maternal fetal medicine at the University of Rochester Medical Center, N.Y. "I think the big message is that glucose control is very important for normal fetal growth," she says. "Even mild forms of gestational diabetes allow elevated levels of glucose to get to the fetus, and that creates hormonal changes in the fetus, in turn leading to excessive growth."
"We know babies who are underweight or overweight have greater risk for health problems in later life, including diabetes," Pressman says. In her experience, most pregnant women, if they are found to have gestational diabetes, are very willing to monitor their diet and make other changes. "Pregnant women are very motivated health-wise," she says.
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Eva Pressman, MD, professor of obstetrics and gynecology and director of maternal fetal medicine, University of Rochester Medical Center, Rochester, N.Y.
Landon, M. The New England Journal of Medicine, Oct. 1, 2009; vol 361: pp 1339-1348.
WebMD Medical Reference "Understanding Gestational Diabetes -- the Basics."
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