Cal Poly contributed to a large, national study that found lifestyle interventions can help pregnant women with overweight and obesity reduce unhealthy weight gain during pregnancy.

Gaining excessive weight during pregnancy increases the risk of serious delivery and birth complications for mothers and their babies, and these risks are compounded in women with obesity.

A new group of National Institutes of Health (NIH)-funded trials — including one conducted by Cal Poly involving Central Coast women — showed that pregnant women can safely limit weight gain with diet, exercise and behavioral interventions. With 1,150 participants, this was the largest set of trials in the U.S. to target pregnancy weight gain in women with overweight or obesity. The trials included diverse socioeconomic groups, which means the findings — published in the journal Obesity— are applicable to a large population.

“It’s been difficult to find ways to help women with overweight or obesity during pregnancy because the recommended weight gain is less than for other women,” said Suzanne Phelan, a professor in the Kinesiology and Public Health Department who directed the Cal Poly study. “Now we can say with some certainty that it’s possible to help women manage their weight during pregnancy, and there are a number of different lifestyle approaches that work.”

The majority of U.S. women of reproductive age have weight issues. Those with overweight or obesity are a critical study group because they have higher rates of excess pregnancy weight gain and of retaining that weight postpartum. They are also more likely to have children with obesity.

Cal Poly’s clinical trial focused on a lifestyle intervention that included meal replacements, physical activity and behavioral strategies. Partnering with Dignity Health and the Community Health Centers, Phelan’s researchers recruited expectant mothers with overweight or obesity to participate.

Half the women received usual prenatal care and additional mailings regarding healthy habits during pregnancy. The others received usual care plus behavioral counseling and meal replacements, which included customized beverages and nutrition bars designed to replace up to two daily meals. They also were given pedometers and urged to progressively increase their activity to 10,000 steps daily. During the course of the seven-year study, the women were weighed at four points from early pregnancy through 12 months postpartum and evaluated for cardiovascular risk.

Compared to those receiving usual care, women getting behavioral counseling and meal replacements gained less weight and were less likely to gain amounts over current guidelines. In addition, behavioral counseling coupled with meal replacements lowered triglycerides and tended to decrease fasting glucose levels and systolic blood pressure. These findings were published in the American Journal of Clinical Nutrition.

“It’s exciting that several lifestyle approaches worked to reduce excess gestational weight gain, including meal replacements, the DASH diet, online interventions and face-to-face interventions,” Phelan said.

Nationwide, about three in five (62 percent) of the women in the intervention groups, versus three in four (75 percent) in the control groups, exceeded the National Academy of Medicine recommendations for pregnancy weight gain. The recommendation is that women with overweight or obesity limit their pregnancy weight gain to 15 to 25 pounds and 11 to 20 pounds respectively, compared to 25 to 35 pounds for non-overweight women. 

Clinical trials were conducted at Northwestern Medicine, California Polytechnic State and Brown universities, St. Luke’s-Roosevelt Hospital and Columbia University, University of Puerto Rico, Washington University in St. Louis, Louisiana State University-Pennington Biomedical Research Center and the Phoenix Indian Medical Center/National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix.