Children of mothers who gain more than the recommended amount of weight during pregnancy are more likely to be overweight at age seven, say researchers from The Children’s Hospital of Philadelphia and the University of Pennsylvania School of Medicine, in a study published today in the American Journal of Clinical Nutrition. Children of mothers who are obese prior to pregnancy and gain excessive weight are at the greatest risk for overweight.

“The earliest determinants of obesity may operate during intrauterine life, and gestational weight gain may influence the environment in the womb in ways that can have long-term consequences on the risk of obesity in children,” said study leader Brian Wrotniak, P.T., Ph.D., of The Children’s Hospital of Philadelphia and the University of Pennsylvania. “Adherence to pregnancy weight gain recommendations may be a new and effective way to prevent childhood obesity, since currently almost half of U.S. women exceed these recommendations.”

The researchers reviewed data from a cohort of 10,226 participants enrolled between 1959 and 1965 in the multicenter National Collaborative Perinatal Project. It was initiated to investigate risk factors for cerebral palsy at 12 U.S. sites. This study looked at the children born at full-term gestation, and researchers evaluated socioeconomic and growth data during gestation, at birth and at age 7.

Maternal data were collected at enrollment by using a questionnaire that included maternal pre-pregnancy weight, age and race. Maternal weight and height were measured at the time of delivery to determine gestational weight gain – the difference between the measured weight at delivery and the reported pre-pregnancy weight.

According to the Institute of Medicine (IOM), which makes recommendations for weight gain during pregnancy, the amount of weight women should gain during pregnancy depends on the mother’s weight status before pregnancy. Women at a healthy pre-pregnancy weight are encouraged to gain 25 to 35 pounds, while women who are overweight should stay between 15 to 25 pounds. Women who are underweight should gain more weight during pregnancy—between 28 and 40 pounds.

Of the women studied by the researchers, 11 percent gained excessive weight, 24 percent gained adequate weight and 65 percent gained insufficient weight. Today, said the researchers, these proportions would be very different, with almost one in two women gaining more weight than recommended during pregnancy.

The authors say that encouraging pregnant women to adopt healthy eating practices and engage in aerobic physical activity could help them achieve appropriate weight gain and also help prevent obesity in their children. They add that benefits would likewise result from healthy eating and exercise before becoming pregnant, as well as reducing postpartum weight retention before a subsequent pregnancy.

Using the IOM guidelines, children whose mothers exceeded the recommended weight gain were 48 percent more likely to be overweight than children whose mothers stayed within the recommended weight gain. The risk of overweight was similar for children born of women who gained insufficient weight compared with mothers who gained appropriate weight during pregnancy.

The researchers add that more research is necessary to clarify whether the association between greater gestational weight gain and increased odds of overweight in offspring is causal, and whether it exists in today’s environment of increasing obesity.

Dr. Wrotniak’s coauthors were Justine Shults, Ph.D., of the Center for Clinical Epidemiology and Biostatistics (CCEB) at the University of Pennsylvania School of Medicine; Samantha Butts, M.D., M.S.C.E., of the Division of Infertility and Reproductive Endocrinology at the University of Pennsylvania School of Medicine; and Nicolas Stettler, M.D., M.S.C.E., of Children’s Hospital and the Penn CCEB.