Women who are overweight before pregnancy can use diet modification and physical activity to safely limit excessive weight gain during pregnancy, according to the combined results from seven NIH-funded randomized controlled clinical trials, including one led by researchers at Columbia University Irving Medical Center.

Excessive weight gain during pregnancy may have multiple effects on the health of the mother and the child. It can increase a woman’s risk of developing diabetes and hypertensive disorders and of delivery by Cesarean section and has been associated with childhood obesity and diabetes. Women carrying extra weight before becoming pregnant are more likely to exceed the CDC’s recommended weight gain—15 to 25 pounds for women who are overweight and 11 to 20 pounds for those with obesity—and further increase the risk of complications. (For women who start out at a normal weight, the recommended weight gain is 25 to 35 pounds.)

The trials enrolled a total of 1,150 women with overweight or obesity in the first or second trimester of pregnancy. Half of the group took part in a diet modification and/or physical activity program to prevent excess weight gain during pregnancy.

On average, the women enrolled in a weight-control program gained less weight—about 4 pounds less—than those who were not enrolled. About 38% of the women enrolled in weight-control programs gained the recommended amount of weight vs 25% of the women in the control group. However, both groups had similar rates of diabetes, hypertension, preeclampsia, and C-sections.

The results were published Sept. 6 in the journal Obesity.

“These findings show that women can control the amount of weight gained during the second and third trimesters of pregnancy using a healthy lifestyle approach,” says Dympna Gallagher, EdD, professor of nutritional medicine at Columbia University Vagelos College of Physicians and Surgeons and an investigator in the clinical trials research group, Lifestyle Interventions for Expectant Moms (LIFE-Moms). “Had the intervention started earlier in pregnancy, such as at the beginning of the first trimester, the impact on limiting excessive weight gain and maternal complications may have been greater.”

Gallagher and Xavier Pi-Sunyer, MD, led the trial at CUIMC that investigated whether intervening to prevent excess weight gain during pregnancy would have an effect on a newborn’s body composition. The CUIMC study, published earlier this year in Obesity, included 210 healthy women with overweight or obesity; half were enrolled in a program that promoted a healthier diet and increased physical activity during the second and third trimesters.

Babies of women enrolled in the diet and physical activity program weighed more at birth than babies of the controls. And though babies in both groups had similar amounts of body fat, babies from the lifestyle intervention group had more lean body mass and bigger heads, suggesting increased brain development.

Longer-term studies are needed, Gallagher says, to determine if having more lean mass at birth benefits the babies later in life.

“Interestingly, we did not find an association between infant lean mass and weight gain during pregnancy, either excessive or within guidelines,” Gallagher says. “This suggests that aspects of the diet and physical activity program other than limiting weight gain may be important for the development of babies with lean mass.”