Comparison of different strategies in prenatal screening for Down′s syndrome

Objective:To assess and compare the effectiveness of three different strategies for prenatal screening for Down′s syndrome(the first trimester test,the second trimester test,and the integrated test) and to determine the most useful way for Down′s syndrome screening.Methods:serum PAPP-A and free β-HCG levels of 7802 pregnant women with 9～13+6 weeks and serum AFP and free β-HCG and free uE3 levels of 11 911 pregnant women with 15～20+6 weeks were detected by time-distinguished fluorescence immunoassay.Down′s syndrome risk value was calculated with lifecycle 3.0 software,with cut-off value of 1∶270.The pregnant women whose value bigger than 1∶270 would be as high risk of Down′s syndrome and needed to have the cordocentesis for fetal karyotype.Results:19 713 pregnant women accepted the Down′s syndrome screening,1059 of which were detected positive for Down′s syndrome with false positive rate of 5.37%(1059/19713).607 cases received fetal karyotype,accounting for 57.32%(607/1059),detecting abnormal fetal chromosome in 24 cases with detecing rate 3.95%(24/607),including 4 cases of Down′s syndrome and 3 cases of 18-trisome.Beside this,5 neural tube defects cases were found in the second trimester test.1 case of Down′s syndrome was confirmed after birth.The three different strategies′(the first trimester test,the second trimester test,and the integrated test) false positive rate were:5.79%,5.10%,4.04%.Conclusion:The integrated test was better than the first trimester test and the second trimester test.