Diet and exercise may stem weight gain of pregnancy, but should begin early

About 26% of women are overweight when pregnant and 25.6% are obese

For years, maternal health experts have worried about a troubling statistic: More than half of all pregnant women in America are overweight or obese when they conceive, putting them and their children at a higher risk of developing diabetes and other health problems.

So about a decade ago, the federal government launched a multimillion-dollar trial to see whether diet and exercise could help overweight women maintain a healthy weight during their pregnancies and potentially reduce their rate of complications. On Thursday, the findings were announced, and the results were mixed: Starting a diet and exercise program around the beginning of their second trimesters helped many women avoid excess weight gain during their pregnancies. But it did not lower their rate of gestational diabetes, hypertension and other adverse outcomes.

Experts said the research was both encouraging and sobering. It confirmed that overweight and obese women can safely limit their pregnancy weight gain with lifestyle interventions. But it also suggests that to improve obstetric outcomes and the health of their babies, women who are carrying extra weight may need to make significant lifestyle changes before they conceive, said Dr. Alan Peaceman, the chief of maternal fetal medicine at Northwestern University Feinberg School of Medicine and the lead investigator of the study, which was published in obesity.

"This is a problem that is more important now than it’s ever been, and it needs to be addressed," he added. "We are going to have to start talking to women who are overweight or obese even before pregnancy and explain to them the risk of that weight on a potential pregnancy."

The new research comes at a critical time. Decades ago, health authorities routinely urged pregnant women to put on enough weight to lower their odds of having underweight babies. But when the obesity epidemic took off in the 1980s and ‘90s, it spared almost no population, including pregnant women. Research by the Centers for Disease Control and Prevention found that the prevalence of obesity among pregnant women climbed by 69 percent from 1993 to 2003. Today about 26 percent of women are overweight when they enter pregnancy and 25.6 percent are obese,according to the latest C.D.C. data.

 

Women in those groups are more likely to exceed the recommended amount of weight gain during pregnancy and to retain that weight postpartum. Among the complications, they are more likely to experience are longer labours, abnormally large babies, hypertension and caesarean deliveries. Obese women also have higher rates of gestational diabetes, miscarriages and pre-term births. And a number of studies show that their children have increased rates of obesity and Type 2 diabetes.

In 2009, the Institute of Medicine issued a report outlining the amount of weight that women should gain during their pregnancies based on their body mass index. Women in the normal weight category should gain between 25 and 35 pounds, the guidelines state, while those who are overweight should add 15 to 25 pounds. Obese women are encouraged to gain no more than 20 pounds during pregnancy.

Over the years, a number of studies looked at whether lifestyle changes could improve health outcomes for expectant mothers with high B.M.I.s. But many of the studies were small, not very rigorous or of poor quality, so the National Institutes of Health set out to fund a large and definitive study in a diverse group of women. The resulting study recruited 1,150 overweight and obese women at seven clinics across the country and randomly assigned them to a control group or an intervention group that followed a variety of diet and exercise strategies. The women were all between nine and 15 weeks pregnant when they joined the study.

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