Background : The ultimate goal in preterm survivors is to promote appropriate growth and neurodevelopment. Breast milk is considered the ideal nutrition for all neonates. For full term infants, breast milk itself is a perfect nutrient resources for several months. However little is known about the nutrient composition of preterm breast milk and it is usually considered that breast milk-fed infants are more growth restricted even with extra supplements compared with preterm formula-fed infants. Objectives: This study aimed to evaluate short-term growth outcomes of preterm infants based on the type of feeding administered. Other secondary outcomes included neonatal morbidities. Methods: All newborn infants born at 34weeks of gestation or birth weight 1,500g and admitted to the neonatal intensive care unit of CHA Bundang Medical Center from February 2016 through February 2017 were eligible. We selected age matched controls in a ratio of 1.5 :1 with preterm formula feeding. We collected the data of gestational age, body weight at birth through 4weeks, perinatal risk factors and neonatal diseases. The breast milk was fortified when reached full enteral feeding(100ml/kg/day) in a dose of adding protein 0.55g per 100ml of human milk. Results: We included 66 preterm infants: 39 in the fortified breast milk-fed group and 27 in the preterm formula-fed group. The overall gestational age and birth weight were 31.5±1.8wks, 1570±360g, respectively. In our study infants the outcome of extrauterine growth for initial 4weeks showed no differences between two groups(1,840±390g vs. 2,040±420g, P=0.091). Neonatal morbidity revealed no significant differences, either. Analysis of the breast milk samples revealed a lower amount of calcium( P0.001), phosphorus( P0.001), magnesium( P0.001) but no differences in protein composition. In breast milk-fed infants, 400IU of vitamin D was supplemented and there was no differences in the incidence of rickets and nephrocalcinosis between two groups. Conclusion: We found that breast milk with standard fortification is not inferior for neonatal growth and morbidity for preterm infants compared with preterm formula. We also analyzed the breast milk composition of mothers who deliver premature infants. We hope that this will serve as a basis for a customized approach to the fortification of breast milk for preterm infants