Assessing Better Bottles for Babies

This study will use a 2 x 2 factorial design to test impact of two intervention strategies (bottle size and bottle opacity) on infant weight gain.

Inclusion Criteria: * Child is 3 days old to 1 month old * Greater than 37 weeks gestational age at birth * Birth weight greater than 3% for sex-specific WHO growth standard * Caregiver must plan to use local clinic as infant's primary medical home for first 6 months of life * Caregiver must speak English or Spanish as primary preferred language * Caregiver age 18 years or older * Caregiver must agree to use intervention bottles assigned during randomization and agree to stop using their existing bottles during the study period Exclusion Criteria: * Multiple gestation * Significant congenital anomaly or acquired or inherited condition directly affecting feeding, physiology, metabolism, or growth * Feeding with soy-based, hydrolyzed, lactose-reduced, or elemental formula * Weight loss greater than 95% for population reference in the first two weeks of life