Neonatal morbidity during NICU stay: Short term clinical outcomes including duration and type of respiratory support and O2 supplementation during the NICU stay, respiratory morbidities such as respiratory distress syndrome, need for surfactant, pulmonary hypertension, and BPD will be obtained from the NICU database. In addition, other short term morbidities such as sepsis, Grade III/IV IVH, NEC, symptomatic patent ductus arteriosus, severe ROP, length of hospitalization and mortality during NICU stay will also be collected from the NICU database.