Objective: To examine the effects of formula, other milks, other liquids, cereals, and other solid foods on growth during infancy.
Study design: Observational cohort study nested within a large (n=17,046), cluster-randomized trial. We compared growth [weight-for-age, length-for-age, and weight-for-length z scores (WAZ, LAZ, WLZ) and head circumference (HC)] during the intervals 1 to 3, 3 to 6, 6 to 9, and 9 to 12 months, using hierarchical multivariate regression to control for size at the beginning of each interval, maternal education, geographic region, and urban versus rural location.
Results: Mixed BF and formula/other milk were associated with significantly higher (versus breast milk only) LAZ at 1 to 3 months (+0.038 and +0.047, respectively). In the 3- to 6-month interval, mixed BF and formula/other milk led to significantly higher WAZ (+0.125 and +0.139) and LAZ (+0.081 and +0.075), whereas cereal intake was associated with large and highly significant reductions in both measures (-0.293 and -0.240) and in HC (-0.291 cm). Mixed BF and formula/other milk continued to have positive albeit smaller associations with WAZ and LAZ in the 6- to 9-month and 9- to 12-month intervals.
Conclusions: Our results confirm the growth-accelerating effects of formula and other milks (versus breast milk) on weight and length gain throughout infancy, with a dose-response gradient and largest associations observed at 3 to 6 months.