Relationship between modifiable factors and late pregnancy physical activity on infant motor development at 12 months of age: findings from a rural city in the Mid-Southern USA

OBJECTIVES: To assess the relationship of infant growth, feeding practices and tummy time to their motor development at 12 months, with a special focus on how maternal physical activity during late pregnancy relates to infants' motor skills. DESIGN: Longitudinal study. SETTING: Rural city in the Mid-Southern USA. PARTICIPANTS: 16 singleton pregnant women in the third trimester and their term infants were recruited, excluding mother-infant pairs with health issues that impact infants' motor development and restrict mothers' physical activity. PRIMARY AND SECONDARY OUTCOME MEASURES: Maternal physical activity and sedentary time during the third trimester were measured using Actigraph activity monitors. Labour nurses measured neonatal birth weight and length using standard procedures. Infants' motor percentiles at 4 and 12 months were measured respectively using the Alberta Infant Motor Scale and Peabody Developmental Motor Scales II test by a licensed paediatric physical therapist. Feeding practices, infants' time spent in different positions and family composition were evaluated separately at 4 and 12 months using a study-specific survey. RESULTS: Infant motor percentiles at 4 months were positively associated with their 12-month motor percentiles (r=0.649, p=0.009). For each additional percentile at 4 months, the mean 12-month percentile increased by 0.4. Motor percentiles at 12 months were also positively associated with infants' birth weight (r=0.553, p=0.026) and length (r=0.637, p=0.008), but not significantly associated with tummy time (r=-0.069, p=0.840). Infant motor percentiles at 12 months were not associated with time spent sedentary (r=-0.134, p=0.634), light activity (r=0.213, p=0.447) or moderate activity (r=-0.050, p=0.858) during the third trimester. At 12 months, breastfeeding status (p=0.576) and having siblings (p=0.230) were not related to motor scores. CONCLUSIONS: Motor percentiles at 4 months, birth weight and length correlated with motor skills at 12 months, whereas tummy time, siblings, and breastfeeding were not significant predictors. Physical activity during pregnancy did not significantly correlate to motor skills at 12 months.