Pregnant women who gain excessive or even appropriate weight, according to current guidelines, are about four times more likely than women who gain inadequate weight to have a baby who becomes overweight in early childhood. The findings, from the Department of Ambulatory Care and Prevention at HMS and Harvard Pilgrim Health Care, appear in the April issue of the American Journal of Obstetrics and Gynecology.
“Maternal weight gain during pregnancy is an important determinant of birth outcomes,” said lead author Emily Oken, an HMS instructor in the department. “These findings suggest that pregnancy weight gain can influence child health even after birth and may cause the obstetric community to rethink current guidelines.”
Oken and colleagues examined data from 1,044 mother–child pairs in Project Viva, a prospective study of pregnant women and their children based at the department’s Obesity Prevention Program. The authors studied whether pregnancy weight gain within or above the recommended range increased the risk of a child being overweight at age 3.
In 1990, the Institute of Medicine (IOM) published guidelines for gestational weight gain (Nutrition During Pregnancy) that were motivated by evidence that low weight gain in pregnant women may cause low birth weight. The guidelines call for smaller gains in mothers with a higher body mass index (BMI) and generally permit greater gains than previous recommendations.
The IOM report remains the standard for clinical recommendations regarding gestational weight gain. Yet some have questioned whether evidence is sufficient that greater gains promote better birth outcomes in modern developed nations.
In this study, 51 percent of women gained excessive weight; 35 percent gained adequate weight; and 14 percent gained inadequate weight, according to the IOM framework. Women with adequate or excessive gain were approximately four times more likely than those with inadequate gain to have an overweight 3-year-old. The authors defined overweight as a BMI greater than the 95th percentile for the child’s age and sex.
Gestational weight gain may be linked to child overweight through several pathways. Mothers who gain weight readily because of genetic or dietary and other behavioral factors may have children who are more likely to gain weight. In addition, the amount of weight gained during pregnancy might alter the intrauterine environment, not only influencing fetal growth, but possibly resulting in persistent programming of child weight.
“It has been 17 years since the IOM came out with its last set of recommendations, before the obesity epidemic hit with full force,” said Matthew Gillman, HMS associate professor of ambulatory care and prevention and senior author of the study. “Now, women are coming into pregnancy at higher weights and likely gaining excessively more than they used to. We need to find out how to counter this trend—but not go too far back in the other direction when women were gaining too little weight.”
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