Abstract: Objective：Retrospectively analyzed the serological screening results of pregnant women in their second trimester, to explore the significance of serological screening. Methods：The concentration of alpha-fetoprotein（AFP），beta subunit of human chorionic gonadotropin（β-hCG） and unconjugated estriol （uE3） was detected in serum of 9 508 pregnant women （15-20+6 gestational weeks） in obstetrics and gynecology department of Beijing Military General Hospital from September 2010 to March 2014. Risks were assessed by combination with maternal age，gestational age and weight of pregnant women. Results：Among all the 9 508 screening women, 743 cases were detected at high risk，and the positive rate was 7.81%. In which，the Down′s syndrome（DS） high-risk rate was 5.92%（563/9 508），the 18-trisome high-risk rate was 0.20%（19/9 508），the neural tube defects（NTD） high- risk rate was 1.69%（161/9 508）. Karyotype analysis of amniotic fluid cells confirmed DS 5 cases，18-trisomy 1 case，other chromosomal abnormalities 12 cases . The study showed that the high-risk rate of DS and NTD between 4 group（aged 20-, 25-,30- and ≥35） were significantly different（P＜0.01）. The DS high-risk rate of pregnant women aged over 35 was significantly higher than that of pregnant women aged under 35（P＜0.01）. One false positive in DS was found in low risk pregnant women during follow-up. Conclusions：Prenatal serological screening has certain guiding significance in reducing birth defects and improving population qualities.

Key words: Congenital abnormalities, Pregnancy trimester, second, Serology, Genetic screening, Prenatal diagnosis