We sought to assess the association between maternal gestational physical activity and insulin action and body composition in early infancy.At 28-32 weeks' gestation, pregnant women participating in an observational study in Sweden underwent assessments of height, weight, and body composition, an oral glucose tolerance test, and 10 days of objective physical activity assessment. Thirty mothers and infants returned at 11-19 weeks postpartum. Infants underwent assessments of weight, length, and body composition.Early insulin response was correlated with total physical activity (r = -0.47; P = 0.007). Early insulin response (r = -0.36; P = 0.045) and total physical activity (r = 0.52; P = 0.037) were also correlated with infant fat-free mass. No maternal variable was significantly correlated with infant adiposity.The relationships between maternal physical activity, insulin response, and infant fat-free mass suggest that physical activity during pregnancy may affect metabolic outcomes in the mother and her offspring.