Analysis of down's syndrome screening and antenatal diagnosis of 3195 cases in the middle period of pregnancy

[Objective] To explore the practical value of Down's screening in the middle period pregnancy in detecting chromosomal disease and congenital birth defect and predicting the outcome of pregnancy. [Methods] Serum AFP and free-β-HCG level of pregnant women(14~20+6 weeks) were detected by time-distinguished fluorescence immunoassay. Down's syndrome risk value was calculated with Multicalc software, its cut-off value was 1:250. The pregnant women whose value are higher than or equal to 1:250 would be at high risk and need to have the cordocentesis for fetal karyotype after 18 weeks. [Results] 3195 pregnant women accepted antenatal screening, 232 cases of them were detected at high risk, and positive rate was 7.3%,including 169 cases of high risk with Down's syndrome(fasle positive rate 5.2%). Fetal karyotypes of 147 cases diagnosed by the cordocentesis, 19 cases with fetal abnormal chromosome, the detectable rate was 12.9%,including three cases of Down's syndrome, a case of 18-trisome and a case of X-trisome. There is signification different in the rate of the abnormal outcome of pregnant women and fetuses in two groups of high risk and low risk of Down's syndrome (30.2% and 12.3% respectively, P 0.05). [Conclusion] The serum AFP and free-β-HCG level of pregnant women during second-trimester were effective indexes to screen abnormal fetus and predict outcome of pregnancy and fetus, which would be a practical method of preventing congenital defect.