MUC1 and Patent ductus arteriosus: We tested several indicators as potential risk factors for moderate/severe BPD; KL-6/7d, KL-6/14d, PDA (lung hemorrhage), mechanical ventilation (days), GA (weeks), weight (g), antenatal steroids, sex, C-section, complicated pregnancy, and Apgar score <3 at 1 minute, and ROC curve analysis was used to set a cutoff value.