PROTOCOL OUTLINE: This is a randomized, double blind study in arms I and II. Patients are randomized to receive either fortified pasteurized donor human milk (arm I) or preterm formula (arm II) as a supplement to mother's milk, if needed. Patients are stratified according to gestational age (less than 26 weeks vs 27-29 weeks) and prior antenatal steroids (yes vs no). Patients are also assigned to groups receiving fortified mother's milk (arm III) and preterm formula only (arm IV).