Basic data and primary and secondary endpoints were collected for both groups by reviewing medical records. The basic data collected included gender, birth weight, gestational age. The primary endpoints were PaO2, carbon dioxide partial pressure (PaCO2) and oxygenation index (OI) 12 and 24 hours after the start of NIV. The incidences of intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL), necrotizing enterocolitis (NEC), bronchopulmonary dysplasia (BPD), and apnea during the first 72 hours were the secondary endpoints. In addition, the treatment effects including duration of NIV, duration of nasal cannula oxygen therapy, length of hospital stay, time to full feeding and maternal high-risk factors related to the parturients, the use rates of antenatal corticosteroid and surfactant and delivery mode were compared between groups.