NPPB and perinatal asphyxia: According to the logistic regression analysis, UCB IL-6, NT-proBNP, pH value, Apgar scores at 1 and 5 min, perinatal asphyxia, initial FiO2, invasive ventilation, surfactant therapy, HsPDA, RF, and IVH were identified as independent risk factors for grading BPD.