Nicolaides Kypros H, Wegrzyn Piotr
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, United Kingdom.
Ginekol Pol. 2005 Apr;76(4):257-63.
In normal pregnancy fetal nuchal translucency (NT) thickness increases with gestation, in trisomy 21 and other major chromosomal defects fetal NT is increased. The risk for trisomies can be derived by multiplying the a priori maternal age and gestation related risk by a likelihood ratio, which depends on the degree of deviation in fetal NT measurement from the normal median for that crown-rump length. In a pregnant population with a mean maternal age of 28 years, using the risk cut-off of 1 in 300 to define the screen positive group would detect about 80% of trisomy 21 fetuses for a false positive rate of 5%. It was estimated that, for a 5.4% false positive rate, 90% of trisomy 21 fetuses could be detected. Prospective studies have demonstrated that such results are achievable by screening with fetal NT and maternal serum free b-hCG and PAPP-A in the first-trimester. It is therefore essential that, in screening, attention is paid to the provision of high quality sonographic and biochemical services for early diagnosis of chromosomal defects.
在正常妊娠中，胎儿颈部半透明带（NT）厚度随孕周增加，而在21三体综合征及其他主要染色体缺陷中，胎儿NT增厚。通过将先验的母亲年龄和孕周相关风险乘以一个似然比，可以得出三体综合征的风险，该似然比取决于胎儿NT测量值相对于该头臀长正常中位数的偏离程度。在平均母亲年龄为28岁的孕妇群体中，使用1/300的风险截断值来定义筛查阳性组，将能检测出约80%的21三体胎儿，假阳性率为5%。据估计，对于5.4%的假阳性率，90%的21三体胎儿能够被检测出来。前瞻性研究表明，通过孕早期检测胎儿NT以及母亲血清游离β-hCG和妊娠相关血浆蛋白-A进行筛查，可实现这样的结果。因此，在筛查中，必须注重提供高质量的超声和生化服务，以便早期诊断染色体缺陷。
