Weight gain in early pregnancy has the greatest impact on infant size at birth, according to a new study published in the journal Obesity. The study is the largest ever analysis of the effect that weight gain in early pregnancy has on infant size.

The study examined 16,218 pregnant mothers throughout the first, second and third trimesters in Tianjin, China to determine the risk of infants’ size at birth. Results found weight gain early in pregnancy, before 24 weeks - regardless of the weight gain later - had the greatest impact on infant size. Infants born to women with weight gain that exceeds the 2009 Institute of Medicine guidelines for weight gain during pregnancy, prior to 24 weeks, were 2.5 times more likely to be born large.

Maternal obesity and weight gain in pregnancy have been strongly linked to the development of overweight and obesity in children, although few studies have examined in-depth gestational weight gain with infant birth weight and childhood obesity. “Obstetrician gynecologists need to begin to educate patients who are pregnant or planning to become pregnant on the implications of weight gain in pregnancy on infant outcomes and the development of childhood obesity,” said Leanne M. Redman, PhD, FTOS, who led the study and serves as Associate Professor & Director of the Reproductive Endocrinology & Women’s Health Lab at LSU’ Pennington Biomedical Research Center.

Overall, women who are pregnant or planning to become pregnant should understand the impact that weight gain has on both short and long-term health risks for their child. Since this period of early pregnancy could have the strongest influence on the development of increased adiposity in the child, it is the opportune time to initiate lifestyle interventions in pregnant women. “International clinicians, clinical researchers and pediatricians should care about this research as findings suggest attention to healthy weight gain early in gestation may be warranted,” said TOS spokesperson Suzanne Phelan, PhD, Professor of Kinesiology, Cal Poly, San Luis Obispo.

In an accompanying editorial published in the journal Obesity, Cheryce L. Harrison, PhD discusses gestational weight gain and its association with infant birth weight, agreeing with the recent Obesity study. “These results validate previous literature in smaller cohorts while notably advancing this field of research in one of the largest, most well-defined mother-infant cohorts,” said Dr. Harrison.