Maternal prepregnancy BMI and GWG, including period-specific GWG, were positively and independently associated with neonatal adiposity. Associations of early and midpregnancy weight gain with neonatal adiposity support the hypothesis that greater maternal weight gain during pregnancy, regardless of prepregnancy BMI, is directly related to offspring adiposity at birth. The Healthy Start study was registered as an observational study at clinicaltrials.gov as NCT02273297.

Objective To examine associations between pregnancy physical activity and neonatal fat mass and fat-free mass, birth weight and small for gestational age (SGA). Methods We analyzed 826 mother-neonate pairs (term births) participating in the longitudinal Healthy Start study. The Pregnancy Physical Activity Questionnaire was used to assess total energy expenditure and meeting American College of Obstetricians and Gynecologists (the College) guidelines for physical activity during early pregnancy, mid-pregnancy and late pregnancy. Models were adjusted for maternal and neonatal characteristics. Results Neonates had mean fat mass of 292.9 grams, fat-free mass of 2,849.8 g, and birth weight of 3,290.7 g. We observed 107 (12.9%) SGA and 30 (3.6%) large-for-gestational age (LGA) births. A significant inverse linear trend between total energy expenditure during late pregnancy and neonatal fat mass (Ptrend = 0.04) was detected. Neonates of mothers in the highest compared to lowest quartile of total energy expenditure during late pregnancy had 41.1 g less fat mass (249.4 vs. 290.5 g; P = 0.03). No significant trend was found with total energy expenditure and neonatal fat-free mass or birth weight. Early-pregnancy and mid-pregnancy total energy expenditure were not associated with neonatal outcomes. No significant trend was observed between late-pregnancy total energy expenditure and SGA (Ptrend = 0.07), but neonates of mothers in the highest compared to the lowest quartile had a 3.0 (95% CI 1.4–6.7) higher likelihood of SGA. Meeting the College’s physical activity guidelines during pregnancy was not associated with differences in neonatal outcomes. Conclusions Increasing levels of late-pregnancy total energy expenditure are associated with decreased neonatal adiposity without significantly reduced neonatal fat-free mass.