Studying Infant Feeding and Growth: Timing is Everything

Association of Infant Feeding Methods and Excess Weight from Birth to Age 6

Objective: To examine the associations between human milk feeding method (at the breast versus bottle) and measures of child adiposity during the first 6 years of life. Study Design: Women 12 months' postpartum who delivered a singleton, liveborn infant at >24 weeks gestation completed a survey assessing infant feeding methods and sociodemographics. Mothers were recontacted when the child was 6 years old for a follow-up study assessing growth (N = 269). Children were categorized as ever or never having excess weight using weight-for-age z-scores (WAZ), weight-for-height z-scores (WHZ), and body mass index-for-age z-scores (BMIZ) from birth to 6 years. Modified Poisson regression estimated associations between the duration of each feeding method (exclusive and combined) with excess weight status. Mixed-effect models estimated associations between feeding methods and trajectories of the outcomes. Results: For all feeding practices, increasing duration (in months) was unassociated with the risk of ever having excess weight by age 6 years. Based on mixed models, longer duration of feeding human milk by any method was associated with lower BMIZ (adj β for 6-12 months versus 0-3 months = -0.50, 95% CI: -0.99 to -0.01) and also with the shape of the BMIZ trajectory curve. No other associations between feeding methods and excess weight outcomes were observed. Conclusions: Longer duration of feeding human milk was associated with lower average BMIZ in early childhood but feeding at the breast and feeding expressed milk were not clearly associated with the outcomes when considered separately. Larger studies would help clarify the associations between these specific feeding methods and outcomes. IRB17-00876.