Performance of first-trimester combined screening in the prediction of fetal Down’s syndrome

Abstract:

Objective：To analyze the performance of first-trimester combined screening in the prediction of fetal Down’s syndrome （DS）. Methods：Totally 7 367 cases met the criteria were collected and their pregnant outcomes were analyzed retrospectively. Pre-diction of DS when using nuchal translucency thickness（NT） alone was compared with that when using first-trimester combined screening. Risk cutoff value of first-trimester combined screening was set at 1∶300 and pregnancy outcomes of high-risk and low-risk objects were compared. Performances of NT and first-trimester combined screening were compared taking NT≥3 mm as positive cri－teria. Results：Among the 7 367 cases，positive rate of first-trimester combined screening was 3.4%（252/7 367） and incidence of actu－al abnormal chromosomes was 0.12%（9/252）. High risk group had higher risk of adverse pregnancy outcomes compared with that of low risk group（adverse pregnancy outcomes：6.0% vs. 1.0‰，P＜0.001；abnormal chromosomes：3.6% vs. 0.1‰，P＜0.001）. When using NT value as the only criterion，detection rate of DS was 77.8% and false positive rate was 4.4%；when using first-trimester combined screening，detection rate of DS was 88.9% and false positive rate was 3.3%. Conclusions：First-trimester combined screening can ef－fectively predict abnormal chromosomes and its effect is superior to that of NT alone，therefore，it is recommended for pregnant woman.