Developmental Trajectories of Bottle-Feeding During Infancy and Their Association with Weight Gain.

Objective: To describe patterns of bottle-feeding across the first year postpartum and explore whether bottle-feeding trajectories are differentially associated with infant weight gain.
Method: Data came from 1291 mothers who participated in the Infant Feeding Practices Study 2. Mothers completed a prenatal questionnaire and monthly surveys of infant feeding and growth between birth and 12 months. Group-based trajectory mixture modeling was used to describe developmental trajectories of bottle-feeding intensities across the first year. Growth curve modeling was used to explore associations between bottle-feeding intensity trajectory group membership and weight-for-age z-score (WAZ) trajectories from birth to 12 months.
Results: Four qualitatively distinct trajectories of bottle-feeding were identified: (1) High-Stable: ∼100% of feeds from bottles across infancy; (2) Rapid-Increase: <30% of feeds from bottles during the neonatal assessment, increasing to ∼100% by 6 months; (3) Gradual-Increase: <10% of feeds from bottles during the neonatal assessment, gradually increasing to ∼100% by 12 months; and (4) Low-Stable: <5% of feeds from bottles across the majority of infancy. Bottle-feeding groups had significantly different WAZ trajectories across infancy; by 12 months, the High-Stable and Rapid-Increase groups had significantly higher WAZs compared with the Gradual-Increase and Low-Stable groups (p < .001). The association between bottle-feeding group membership and WAZ trajectories was not confounded by sociodemographic characteristics or the extent to which infants received breast milk.
Conclusion: High-intensity bottle use during early infancy may place infants at higher risk for excess weight gain. Supports and policies that help mothers delay high-intensity bottle use until later infancy are warranted.