超声检查胎儿颈项透明层厚度在筛查胎儿染色体异常中的价值

Value of nuchal translucency thickening in the fetal chromosome abnormality screening

目的 通过对超声检查出的颈项透明层（NT）增厚胎儿进行染色体核型分析,评价超声检查NT增厚在筛查胎儿染色体核型异常中的作用.方法 2010年1月至2012年8月首都医科大学附属北京妇产医院于孕11～13周＋6行超声胎儿NT检查的孕妇共14 881例,其中胎儿NT≥2.5mm 的118例纳入本研究,118例孕妇中单胎妊娠113例（95.8％）,双胎妊娠5例（4.2％）.其中的108例孕妇行介入性产前诊断,对胎儿行染色体核型分析.结果 （1）染色体核型分析：108例（91.5％,108/118）孕妇进行了胎儿染色体核型分析,其中88例染色体核型分析未见异常;20例染色体数目异常,染色体异常检出率为18.5％（20/108）.（2）NT≥2.5 m m筛查胎儿染色体异常的诊断值：其灵敏度为44％、特异度为99％、假阳性率为1％、假阴性率为56％、总符合率为99％,阳性预测值为19％、阴性预测值为100％.（3）88例染色体核型分析未见异常的胎儿中,其中72例（82％）系单纯NT增厚,无结构异常;余16例胎儿（18％）同时合并结构畸形或胎死宫内.（4）10例未行染色体核型分析的胎儿中,8例因超声检查发现畸形而终止妊娠,2例胎死宫内.（5）5例双胎妊娠均为双绒毛膜性,均为双胎之一出现NT增厚,染色体核型系1例双胎之一为21三体,余4例双胎胎儿染色体核型正常,其中3例双胎均活产;1例双胎之一胎儿孕中期超声诊断为腹裂、内脏外翻畸形,之后发生胎死宫内,另一胎儿足月活产分娩.（6）118例孕妇中35例（29.7％）进行了唐氏综合征筛查,其中1例孕妇结果显示高风险,胎儿染色体核型分析证实为21 三体.余34例孕妇均为唐氏综合征筛查低风险,胎儿染色体核型均正常.结论 孕11～13周＋6超声检查胎儿NT增厚,提示胎儿有染色体异常的可能,同时提示胎儿可能存在其他结构畸形,因此胎儿NT增厚是一个有效的产前筛查指标.

Objective To investigate the value of nuchal translucency（NT） thickening in the fetal chromosome abnormality screening.Methods The 14 881 pregnant women received NT measurement in 11-13 ＋6 weeks at Beijing Obstetrics and Gynecology Hospital from January 2010 to August 2012.The 118 fetuses whose NT≥2.5 mm were recruited.One hundred and eight （91.5％,108/118）of them accepted invasive procedure and karyotype analysis.Results （1） Chromosome karyotype analysis：113 singleton pregnancies （95.8％） and 5 twin pregnancies （4.2％） whose NT thickened from 2.5 mm to 11.0 mm were advised karyotype analysis.The 108 pregnant women accepted karyotype analysis.Among them,88 had normal chromosome karyotype,and 20 had chromosome abnormalities.The detection rate was 18.5 ％ （20/108）.（2） The sensitivity,specificity,false positive rate,false negative rate,total consistent rate,positive predictive value and negative predictive value of prenatal screening of chromosome abnormalities for NT ≥ 2.5 mm were 44％,99％,1％,56％,99％,19％ and 100％,respectively.（3） Among the 88 fetuses who had normal karyotype,72 （82％） had isolated thickened NT,while 16 （18％） had fetal structural malformation or intrauterine demise.（4） Among the 10 pregnant women who did not accept fetal karyotype analysis,8 terminated pregnancy because of fetal structural malformation,and the other 2 fetuses died in uterus.（5）All of the 5 twin pregnancies were dichorionic twins,and one of the twins had thickened NT.Among the 5 twin pregnancies,one fetus was trisomy 21 and others had normal karyotype.3 twin pregnancies who had normal chromosomes gave live birth.And the other had a gastroschisis and exstrophy deformity fetuse.This fetuse died in uterus and remaining fetuse had full-term live birth.（6） 35 （29.7％） pregnant women received second trimester Down＇s syndrome serum screening.One was high risk and was proved a trisomy 21 pregnancy.Thirty-four were low risk and had normal chromosome karyotype.Conclusion NT thickening may indicate fetal chromosome abnormalities or other structural malformations.It is a useful prenatal screening indicator.