Maternal prepregnancy obesity and achievement of infant motor developmental milestones in the upstate KIDS study.

Objective: Maternal prepregnancy obesity is associated with several poor infant health outcomes; however, studies that investigated motor development have been inconsistent. Thus, maternal prepregnancy weight status and infants' gross motor development were examined.

Methods: Participants consisted of 4,901 mother-infant pairs from the Upstate KIDS study, a longitudinal cohort in New York. Mothers indicated dates when infants achieved each of six gross motor milestones when infants were 4, 8, 12, 18, and 24 months old. Failure time modeling under a Weibull distribution was utilized to compare time to achievement across three levels of maternal prepregnancy BMI. Hazard ratios (HR) below one indicate a lower "risk" of achieving the milestone and translate to later achievement.

Results: Compared to infants born to thin and normal-weight mothers (BMI < 25), infants born to mothers with obesity (BMI > 30) were slower to sit without support (HR = 0.91, P = 0.03) and crawl on hands and knees (HR = 0.86, P < 0.001), after adjusting for maternal and birth characteristics. Increased gestational age was associated with faster achievement of all milestones, but additional adjustment did not impact results.

Conclusions: Maternal prepregnancy obesity was associated with a slightly longer time for infant to sit and crawl, potentially due to a compromised intrauterine environment or reduced physically active play.