Abstract: Background：Fetal lung development is later than other organs, and the maturity of lung development is closely related to pregnancy outcome. Objective：To investigate the relationship between the ratio of systolic acceleration time/ejection time (AT/ET) of fullterm fetal main pulmonary artery ultrasound and neonatal lung maturity and its predictive value. Design：Casecontrol study. Methods：Pregnant women who underwent ultrasound examination of fetal main pulmonary arteries in Xinxiang Central Hospital of Henan Province from October 2019 to October 2020 were taken as the research objects. According to fetal amniotic fluid or tracheal aspiration liquid lamellar bodies (LB)≥50×109·L-1 after delivery, they were divided into mature and immature groups. The clinical data and AT/ET ratio of fetal main pulmonary artery were compared between the two groups. Multivariate logistic regression analysis was used to analyze the factors affecting neonatal lung maturity. Spearman correlation analysis to explore the correlation between AT/ET ratio and neonatal lung maturity. ROC curve was drawn to analyze the predictive value of AT/ET ratio on neonatal lung maturity. Main outcome measures：The relationship between AT/ET ratio of fetal main pulmonary artery and neonatal lung maturity. Results：Ultrasound images of 102 pregnant women and their pulmonary aorta and LB data of newborns were analyzed in this paper, aged from 23 to 36 (29.4±1.0) years, with 37+138+6 (38.3±0.1) weeks of ultrasonic examination of main pulmonary artery. There were 76 cases in mature lung group and 26 cases in immature lung group. There were significant differences in nutritional status, fetal respiratory motor score, PSV and AT/ET in the middle of fetal main pulmonary artery between the two groups (P<0.05). Multivariate logistic regression analysis showed that AT/ET in the middle segment of fetal main pulmonary artery was an independent factor affecting neonatal lung maturity (OR=0.881, 95%CI:0.6780.983). Spearman correlation analysis showed that AT/ET ratio in the middle of fetal main pulmonary artery was positively correlated with neonatal lung maturity (r=0.678, P=0.003). ROC curve showed that the best cutoff value of AT/ET in the middle of fetal main pulmonary artery for predicting neonatal lung maturity was 0.22. At this time, the sensitivity was 92.1% (95%CI：84.1%97.4%), the specificity was 84.6% (95%CI:70.9%93.4%), and the AUC was 0.818 (95%CI:71.5%92.7%). The kappa value of lung maturity predicted by AT/ET ratio was 0.812 (P<0.05). Conclusion：AT/ET in the main pulmonary artery of fullterm fetus is closely related to the lung maturity of newborns, and has certain predictive value for the lung maturity of newborns.

Key words: Term fetus, Main pulmonary artery ultrasound, Systolic acceleration time/ejection time, The lung maturity of the newborn