Treatment for mild gestational diabetes reduced risk for cesarean sections, other birth risks

The treatment of mild gestational diabetes in pregnant women resulted in fewer cases of cesarean deliveries, fetal overgrowth, shoulder dystocia and hypertensive disorders associated with larger-than-average infants, according to data published in The New England Journal of Medicine today.

Whether or not the treatment of pregnant women with gestational diabetes for their high blood glucose levels would provide worthwhile benefits has been a longstanding debate among physicians. Despite some organizations that advocate screening, the U.S. Preventive Services Task Force’s 2008 guidelines suggest the data is insufficient to support screening for and treatment of gestational diabetes.

“This study is important because it clearly indicates the value to mothers and their newborns of the screening for and treatment of diabetes-like conditions provoked by pregnancy,” John M. Thorp, MD, McAllister distinguished professor of obstetrics and gynecology at the University of North Carolina School of Medicine at Chapel Hill, said in a press release. “Our work resolves a 40-year controversy in women’s health and should be immediately helpful to both pregnant women and the clinicians caring for them.”

Multicenter, randomized trial

Thorp and colleagues randomly assigned 958 women to treatment with dietary intervention, self-monitoring of blood glucose and insulin therapy (n=485) or to a control group (n=473). To mask the status of controls, researchers included an additional 931 women with normal oral-glucose tolerance test results to the control group.

No significant differences were found between the treatment and control group for the frequency of the composite outcome of stillbirth or perinatal death and neonatal complications (32.4% vs. 37%; P=.14). No perinatal deaths occurred among either group.

Significant reductions were found among women in the treatment group vs. women in the control group for mean birth weight (3,302 g vs. 3,408 g), neonatal fat mass (427 g vs. 464 g), the frequency of large-for-gestational age infants (7.1% vs. 14.5%), birth weight >4,000 g (5.9% vs. 14.3%), shoulder dystocia (1.5% vs. 4%) and cesarean delivery (26.9% vs. 33.8%).

In addition, when compared with controls, reduced rates for preeclampsia and gestational hypertension were found in women included in the treatment group (8.6% vs. 13.6%; P=.01).

“These findings complement the ongoing analysis of the Hyperglycemia and Adverse Pregnancy Outcome study data, which is focused on developing an international consensus for the diagnosis and treatment of carbohydrate intolerance during pregnancy,” the researchers concluded.

In an accompanying editorial, David A. Sacks, MD, of the department of Obstetrics and Gynecology at Kaiser Foundation Hospital in California, wrote, “Although further research is needed, a focus on monitoring and minimizing excessive weight gain during pregnancy for all women seems to be a prudent and inexpensive policy, the benefits of which, for both mother and baby, may extend far beyond birth.” - by Jennifer Southall

Landon MB. N Engl J Med. 2009;361:1339-1348.

More In the Journals summaries>>

Results of the HAPO study indicate that levels of maternal glycemia lower than those diagnostic of diabetes are associated with risks of adverse perinatal outcomes. The result of the National Institute of Child Health and Human Development-funded randomized, controlled trial of 'mild gestational diabetes' reported in this week's New England Journal of Medicine and a previous randomized, controlled trial of treatment of mild gestational diabetes performed in Australia confirm that there is benefit from treatment. Recruitment processes and glycemic values of participants in the randomized, controlled trials and the HAPO observational study were not identical, but there was much overlap. Therefore, using outcome-based criteria for the diagnosis of gestational diabetes that will soon be recommended by a consensus panel of international experts and the randomized, controlled trial results, we can be confident that pregnancies with a diagnosis of gestational diabetes are at risk for adverse outcome, and that treatment, primarily lifestyle and diet, can reduce the risk.

– Boyd E. Metzger, MD

Tom D. Spies professor of Metabolism & Nutrition, Northwestern University Feinberg School of Medicine

The authors found that infants of women with mild gestational diabetes defined by fasting glucose <95 mg/dL remain at significant risk for adverse outcomes. Those not treated, largely with insulin, had excess fetal overgrowth, shoulder dystocia, cesarean delivery and preeclampsia. The dilemma not fully addressed is, however, the authors' decision not to disclose the results of oral glucose-tolerance tests to caregivers or subjects in the control group in order to minimize the likelihood of self-treatment, explaining that this would lead to a 'limitation,' so that they 'could not assess glycemia in women in the control group.' Thus, there is a very real ethical dilemma to the reader, although curiously this was not addressed either by the authors of the article or of the accompanying editorial. In the current era of conflicts of interest, we are again reminded of the very real conflict between the roles of the academic physician as experimentalist and as physician and wonder whether this experiment, perhaps carried out among women in disadvantaged communities (as suggested by the .50% prevalence of Hispanic women in the population), truly achieved clinical equipoise. (Gifford F. BMJ. 2001;322:795).

– Zachary T. Bloomgarden, MD

Endocrine Today Editorial Board member