Breastfeeding and motor development in term and preterm infants in a longitudinal US cohort.

The relation between breastfeeding and early motor development is difficult to characterize because of the problems in existing studies such as incomplete control for confounding, retrospective assessment of infant feeding, and even the assessment of some motor skills too early. We sought to estimate associations between infant feeding and time to achieve major motor milestones in a US cohort. The Upstate New York Infant Development Screening Program (Upstate KIDS Study) enrolled mothers who delivered live births in New York (2008-2010). Mothers of 4270 infants (boys: 51.7%) reported infant motor development at 4, 8, 12, 18, and 24 mo postpartum; information on infant feeding was reported at 4 mo. Accelerated failure time models were used to compare times to standing or walking across feeding categories while adjusting for parental characteristics, daycare, region, and infant plurality, sex, rapid weight gain, and baseline neurodevelopmental test results. Main models were stratified by preterm birth status. The prevalence of exclusive breastfeeding in preterm infants was lower than in term infants at 4 mo postpartum (8% compared with 19%). After adjustment for confounders, term infants who were fed solids in addition to breast milk at 4 mo postpartum achieved both standing [acceleration factor (AF): 0.93; 95% CI: 0.87, 0.99] and walking (AF: 0.93; 95% CI: 0.88, 0.98) 7% faster than did infants who were exclusively breastfed, but these findings did not remain statistically significant after correction for multiple testing. We did not identify feeding-associated differences in motor milestone achievement in preterm infants. Our results suggest that differences in feeding likely do not translate into large changes in motor development. The Upstate KIDS Study was registered at clinicaltrials.gov as NCT03106493.