孕11～13＋6周超声筛查胎儿21-三体综合征的研究

目的探讨孕11～13＋6周（胎儿头臀长45~84mm）超声筛查胎儿21-三体综合征的可行性。方法随机对3000例孕中2342例孕11～13＋6周的胎儿进行超声筛查,早孕期鼻骨均做＂有或无＂的鉴定。结果鼻骨缺失的胎儿21-三体综合征的阳性预测值达50%;孕早期鼻骨长度与颈项透明层厚度（NT）之间无相关性;孕早期鼻骨长度与双顶径呈线性增长。结论孕早期鼻骨的缺失对21-三体综合征有较高的阳性预测值,一旦超声诊断鼻骨缺失,均应进行细胞学检查;鼻骨与NT作为预测21-三体综合征风险的独立因素,孕早期鼻骨长度与双顶径呈线性增长,孕早期鼻骨的长度对预测21-三体综合征没有意义。

Ultrasonographic Screening for Trisomy 21 After 11 to 13+6 weeks of Gestation

Objective To find a practical method for uhrasonographic using nasal bone assement after 11 to 13 ＋6 weeks of gestation. Methods screening for Trisomy 21 The risk of Trisomy 21 based on whether the nasal bone was present or absent and the length of nasal bone. Results First trimester nasal bone length did not play a prominent role in ultrasonographic screening for trisomy 21 was predicted, but once the nasal bone was absent, it had a positive predictive value of 50%. There was no relationship between nasal bone and nucal translucency. Nucal translucency and other uhrasono- graphic markers must be taken into acount when the risk of Trisomy 21 was predicted. The length of nasal bone increased linearly with biparietal diameter in first the trimester. Conclusion Presence or absence of the nasal bone should be noticed when doing ultrasonigraphic screening in the first trimester. Confident identification of an absent nasal bone has a high positive predictive value for trisomy 21 in the first trimester. Once a fetus is identified with an absent nasal bone, it shoud be provided with a cy- tological examination. NB and NT can be used as two independent ultrasononographic factors during screening for Trisomy 21. Nasal bone length increases linearly with biacrominal diameter in the first trimester.