ALB and Patent ductus arteriosus: These included base excess, WBC < 5 × 109/L, vasoactive drugs before NEC, gestational age, serum albumin, sepsis, birth weight, PH < 7.25, hemoglobin, portal vein gas, feeding speed > 25 ml/(kg day), type-2 respiratory failure, use of drugs to close PDA before NEC, and frequent sleep apnea, which were used as the final model for further analysis.