Abstract: Objective To explore the association between screening for Down's syndrome and adverse pregnancy outcomes. Methods Retrospective cohort study was conducted in Beijing Chaoyang Hospital covering pregnant 7 682 pregnant women from Mar 31, 2014 to Apr 29, 2021 in a continuum period. Results The prevalence of high screening risk was 6.40% (492 cases) and the incidence of adverse pregnancy outcome was 1.30%(100 cases). The incidence of adverse outcome (4.27%) in high risk group was significantly higher than that in low risk group (1.10%). After adjusting for diabetes, family history of hereditary diseases, smoking and drinking alcohol, the incidence odds of adverse outcomes for high screening risk subjects was 4.022 times (95% CI:2.405-6.442) as that for low risk. The high Down's syndrome risk score meant high incidence of adverse outcomes(P＜0.001). The incidences of malformations, chromosome abnormalities and stillbirth for high screening risk subjects were higher than those for low risk. The incidence odds of adverse outcomes increased to 1.019 times with the increase of 1 ng/mL for AFP and 2.258 times with the increase of 1 for AFP MOM. The incidence odds of adverse outcomes declined to half with the increase of 1 ng/mL for uE3 or uE3 MOM. Conclusions Down's syndrome screening high risk is indicators for organ malformations, limb deformity, chromosome abnormalities and still birth. High level of AFP and low level of uE3 may increase the occurrence of adverse pregnancy outcomes.

Key words: second trimester serum screening for Down's syndrome, adverse pregnancy outcomes, AFP, uE3