With the decrease of vascular resistance, the decrease of pulmonary circulation pressure and the maturation of renal clearance, the level of NT-proBNP gradually decreased and gradually stabilized.9,12 The ROC curve analysis showed that the area under the ROC curve of PDA after three days of birth was 0.949, the critical value was 6,411pg/mL, the sensitivity was 92.3%, and the specificity was 92.9%. This evidence concerns the gene NPPB and Patent ductus arteriosus.