Offspring-sex modifies the association between early-pregnancy adiposity and 2-year-old total physical activity - The Glowing Study.

Background: Rodent models suggest that in utero exposure to under and overnutrition programs offspring physical activity (PA) behaviors. Such nexus has not been established in humans. This study evaluated the association of early pregnancy maternal adiposity with offspring PA at age 2 years (2-yo-PA) taking into consideration prenatal and postnatal factors. Methods: Women (n=153) were enrolled early in pregnancy (<10 weeks). At enrollment, maternal adiposity [air displacement plethysmography, fat mass index (FMI, kg/m 2 )] and PA (accelerometers, activity counts) were measured, and age, race, and education self-reported. Gestational weight gain was measured at the research facility. Offspring birthweight and sex were self-reported. At age 2 years, parental feeding practices (child feeding questionnaire) were assessed, whereas anthropometrics (length and weight) and physical activity (accelerometers) were objectively measured. Offspring body mass index z-scores were calculated. Generalized linear regression analysis modeled the association of maternal FMI and 2-yo-PA [average activity counts (AC) 4 /day]. Results: There was an interaction between maternal FMI and offspring sex in association with 2-yo-PA (β= -1.03, p= 0.030). Specifically, 2-yo-PA was lower in girls compared to boys when maternal FMI was ≥7 kg/m 2 . Maternal PA early in pregnancy positively associated with 2-yo-PA (β= 0.21, p= 0.005). In addition, children born to women with college education tended to be more active compared to children born to women without college education (β= 3.46, p= 0.059). Conclusions: Sexual dimorphism was observed in the associations of maternal adiposity with 2-yo-PA, with girls being less active compared to boys only when maternal FMI was ≥7 kg/m 2 .