超声在孕11-13^(+6)周筛查21-三体综合征中的作用

Ultrasound screening for trisomy 21 syndrome at 11-13^(+6) gestational weeks

目的:探讨孕早期超声测量胎儿鼻骨和颈项透明层厚度(NT)在筛查21-三体综合征中的作用。方法:对在苏州市母子医疗保健中心建卡的孕11-13+6w的孕妇,随机检查3000例,重点对胎儿的颈项透明层厚度和鼻骨进行评估,并与细胞遗传学实验室确诊结果相对照。结果:除658例因体位等原因未检测出鼻骨或NT外,共成功检查出NT及鼻骨2342例。孕妇的平均年龄为26.4岁(21~42岁),大于等于35岁占总数的2%。110例NT>3.0,2例鼻骨缺失,2例被确诊为21-三体,2例为18-三体,1例为13-三体,另4例胎儿为先天性心脏畸形。在上述2342例中,只有1例正常胎儿存在鼻骨缺失,而其NT值仍然>3.0。所以单独以鼻骨缺失为标准,21-三体的检出率为50%;单独以NT增厚为标准,21-三体的检出率为1.8%,两者相比有显著差异(P<0.01)。但通过NT来预测胎儿其他异常方面,其敏感性为64.3%,特异性为95.7%,阳性预测值8.2%,阴性预测值为99.8%,准确性为95.5%,较之鼻骨缺失,有更大的临床意义。结论:鼻骨缺失对诊断21-三体的敏感性要高于NT检查;但是,用NT增厚来预测胎儿其他方面畸形,仍有重要的临床意义。我们认为:鼻骨检测和NT测量相结合,对胎儿21-三体及其他畸形的筛查更有意义。

Objective：To evaluate ultrasound examination （fetal nasal bone and NT） in screening for trisomy 21 syndrome at 11 - 13 ＋ 6 gestational weeks. Methods：2342 pregnant women registered at Mother and Children＇s Health Care Center in our hospital were ex- amined at 11 - 13＋6 gestational weeks. Both fetal nasal bone and NT were evaluated by two qualified experts. The diagnosis of trisomy 21 syndrome was confirmed by cytogenetic laboratory in our hospital. Results：From Nov, 2006 to Dec,2007, fetal nasal bones and NTs had been successfully examined in 2342 pregnancies with 48 pregnant women older than 35 years old （2%）. Among 2342 fetuses, 110 NT were moreathen 〉 3.0 mm, 2 without nasal bone. Based on Lab results, 2 were diagnosed as trisomy 21 syndromes, another 2 were tri- somy 18 sydrome, 1 was trisomy 13 syndrome, and another 4 were congenital cardiac malformation. Among these fetuses, only one nor- mal fetus had no nasal bone, while its NT〉 3.0 mm. Therefore, using ＂absent nasal bone＂ to evaluate trisomy 21 syndrome, the detec- tion rate was 50 %, and using NT 〉 3.0 mm was 1.8 %. Significant difference existed between these two methods （ P 〈 0.01）. Howev- er, NT hads higher clinic significance in screening for other fetal abnomudities, with its sensitivity of 64.3%, specificity of 95.7%, PPV of 8.2%, NPV of 99.8%, and accuracy of 95.5%. Conclusion：According to our study, absent nasal bone is an important ultrasound maker in screening for trisomy 21 syndrome. Even though, NT still has higher clinic significance in screening for other abnormalities. So, when we are screening for trisomy 21 syndrome and otber abnormalities, both nasal bone and NT should be taken into consideration.