Physical activity in pregnancy and neonatal body composition: the Healthy Start study.

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 (College) guidelines for physical activity during early pregnancy, midpregnancy, and late pregnancy. Models were adjusted for maternal and neonatal characteristics.
RESULTS: Neonates had mean fat mass of 292.9 g, 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 neonates. A significant inverse linear trend between total energy expenditure during late pregnancy and neonatal fat mass (Ptrend=.04) was detected. Neonates of mothers in the highest compared with the lowest quartile of total energy expenditure during late pregnancy had 41.1 g less fat mass (249.4 compared with 290.5 g; P=.03). No significant trend was found with total energy expenditure and neonatal fat-free mass or birth weight. Early-pregnancy and midpregnancy total energy expenditure were not associated with neonatal outcomes. No significant trend was observed between late-pregnancy total energy expenditure and SGA (Ptrend=.07), but neonates of mothers in the highest compared with the lowest quartile had a 3.0 (95% confidence interval 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.
CONCLUSION: Increasing levels of late-pregnancy total energy expenditure are associated with decreased neonatal adiposity without significantly reduced neonatal fat-free mass. LEVEL OF EVIDENCE: II.