A strict feeding protocol is followed for all study infants. Depending on the birth weight and gestational age, a certain amount of breast milk is initiated after the infant tolerated one trial of distilled water. On the first day, 1 mL/kg - distilled water was given twice, followed by breast milk. The amount of feeding was advanced slowly if tolerated, with no more than 20 mL/kg/day of increment per feed. An oral intake of 100 mL/kg/d is defined as complete enteral feeding. Feeding was stopped if there was any sign of feeding intolerance, defined as the presence of gastric aspirate in the amount that was more than half of the previous feeding, twice, with abdominal distension. Infants who weighed under 1,000gm received total parenteral nutrition (TPN) until half of the calories were supplied by oral route. The same attending physician is in charge of the care of the infants during their hospital stay. The residents who rotated through the NICU provided the care following established protocols in the unit. Definition of prenatal steroid, small for gestational age, prolonged rupture of amniotic membrane, chorioamnionitis, asphyxia, respiratory distress syndrome, patent ductus arteriosus, intraventricular hemorrhage (IVH), sepsis; indication of surfactant and indomethacin are described as in our previous study. [16 ] There were no modifications in any management protocols, clinical practices, equipment, infrastructure, or any other elements in the unit during the study period, and all the protocols got consensus in the eight centers after several discussion.