Abstract: Objective：To analyze the correlation between the results of serologic Down′s screening in the second trimester and the expected age, weight and adverse pregnancy outcome, so as to provide reference for clinical diagnosis and prediction. Methods：Through the maternal and child health information management platform of Henan Province, 554 751 pregnant women in 1 697 hospitals in 18 cities of Henan Province were selected for Down′s screening examination and terminated pregnancy in 2017 and were divided into low-risk group (control group), critical risk group and high-risk group according to the results of Down′s screening. Statistical analysis was made on the expected age, weight and the incidence of miscarriage, premature delivery and small for gestational age infants in different risk groups. Results：①The expected age and weight of pregnant women are correlated with the results of Down′s screening. With the increase of age，the proportion of pregnant women with abnormal risk of 21-trisomy and 18-trisomy also increases. Compared with the control group，the weight of pregnant women in the observation group increased and the difference was statistically significant (P＜0.05). ②The differences between the incidence of miscarriage, preterm labor and small for gestational age infants in the control group and the observation group of 21-trisomy and 18-trisomy are not statistically significant (P＞0.05). The incidence of abortion, preterm delivery and small for gestational age infant in the high-risk group of neural tube defect (NTD) was higher than that in the control group, and the difference was statistically significant (P＜0.05). Conclusions：In the second trimester, serologic Down′s screening not only can screen aneuploidy chromosome and NTD of fetuses, but also serve as an auxiliary examination to predict adverse pregnancy outcomes, especially for pregnant women with high risk of NTD, and has guiding significance for the prevention of birth defects in pregnant women.

Key words: Pregnancy trimester, second, Maternal serum screening tests, Critical risk, High risk, Pregnancy outcome