- Supplemental Diet (minimal maternal milk) Group: Infants whose mothers initially choose to provide breast milk and begin pumping will be re-screened for eligibility at least weekly until the infant is 21 days old. If the mother stops expressing milk at any point prior to the infant's 21st day of life, her infant will be eligible for randomization. In addition, those whose mothers are providing less than 20% of the infant's dietary needs (averaged over past 5 days) when the infant reaches 21 days of age will be eligible for randomization at this point. No infant will be randomized after reaching 21 days.