Progress Toward Discerning The Aetiology Of Orofacial Clefts

Objective:Compare the detection rate of Down' s syndrome by maternal serumscrenning on different gestational age . And try to find the most sensitiveperiod for prenatal screen .Methods: we reviewed 6907 midpregnant serum screening results that carriedon 15～20 weeks' gestation. Those who were found high risk of Down'ssyndrome pregnancies had been confirmed by amniocentesis. And we comparedthe false positive rate (FPR)among different gestational weeks withinidentical maternal age.Results: Using a 1/250 risk cut-off, a detection rate of 4.75% (95% CI= 71.5-74.3%; was achieved with a false-positive rate of 4.64% (95% CI= 6. 71-8.3%). 328 cases were found with higt risk of Down's syndromepregnancy, and the following amniocentesis confirmed 8 case. The lowest FPRof Down' s syndrome maternal serum screening occurred at 16 to 19 weeks'gestation.Conculsions:0ur data suggest that maternal serum screening for Down'ssyndrome should be done between 16 and 19 weeks' gestation.