新生儿先天愚型占活产婴儿的1‰,由于今后10年35～49岁妇女的增加,其发病率将有所上升。目前,多数孕妇于妊娠中期常规做超声检查,可显示某些可疑先天愚型征缘。先天愚型胎儿在超声检查时显示以下典型表型特征:颈背部皮褶增厚、第五指中节指骨骨化中心发育不良及长骨较短。有人发现孕15～20周时,先天愚型胎儿颈背部皮褶厚度超过6mm 者占43％(9/21) ,而正常胎儿不到0. 1％。其他研究者报道结果不一,阳性率在9％～55％,假阳性率可达9％。约60％的先天愚型患儿第五指中节指骨发育不良,导致指弯曲者占50％。Benacerraf 等检查了 The prevalence of Down’s syndrome is 1 ‰ of live births, and the incidence will increase due to the increase of women aged 35-49 over the next 10 years. At present, the majority of pregnant women do routine ultrasound during the second trimester of pregnancy, may show some suspicious spirit of asceticism. Down’s Fetal Fetal Ultrasound examination showed the following typical phenotypic features: neck dorsal skin fold thickening, the middle finger phalanges ossification center dysplasia and long bones short. It was found that 15 to 20 weeks of pregnancy, Down’s neck fold skin fold more than 6mm accounted for 43% (9/21), while less than 0.1% of normal fetuses. Other researchers reported mixed results, with a positive rate of 9% to 55% and a false positive rate of 9%. About 60% of children with idiopathic obstetrics have phalangeal phalanges in the fifth finger, resulting in 50% finger flexion. Benacerraf checked