Abstract: Objective To explore the application value of automatic ultrasound analysis of the fetal lung in predicting fetal lung maturity in late pregnancy. 
Methods A total of 80 singleton pregnant women delivered in our hospital were given automatic ultrasound analysis of the fetal lung to compare the differences of pulmonary ultrasound parameters between neonatal respiratory distress syndrome(NRDS) and non-NRDS. 
Results Among 80 newborns, 34 cases developed NRDS. The left lung volume(LLV), right lung volume(RLV), total lung volume(TLV) and fetal lung to body weight ratio(FLB) of NRDS newborns were (33.03±3.50) cm3,（44.07±3.16）cm3,（75.57±4.69）cm3and （0.25±0.04）cm3/10 g, respectively, which were significantly lower than those of non NRDS newborns ［(35.12±2.84) cm3, (46.68±3.19) cm3, (81.95±6.03) cm3 and (0.28±0.05) cm3/10 g, respectively］. (P＜0.05). The pulsatile index (PI) and resistance index (RI) of pulmonary artery blood flow parameters in NRDS newborns were (2.14±0.29) and (0.92±0.12) respectively, which were significantly higher than those in non-NRDS newborns ［(2.00±0.28) and (0.83±0.08)］(P＜0.05). There was no significant correlation between PI, RI and LLV, RLV and TLV (P＞0.05), but there was a negative correlation between PI, RI and FLB (r=-0.485 and -0.401, P＜0.05). The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of automatic ultrasound of the fetal lung in predicting fetal lung maturity were 91.18%, 91.30%, 91.25%, 88.57% and 93.33%, respectively. 
Conclusion Automatic ultrasound analysis of the fetal lung can effectively predict fetal lung maturity in late pregnancy, which is worthy of clinical use.

Key words: late pregnancy, ultrasonography, fetal lung maturity