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Title: [Analysis of copy number variation by CMA in fetus with increased nuchal translucency].
Author: Du L, Xie HN, Zheng J, He M.
Journal: Zhonghua Fu Chan Ke Za Zhi; 2018 Oct 25; 53(10):671-676. PubMed ID: 30369122.
Abstract:
Objective: To investigated the clinical value of chromosomal microarray analysis (CMA) in fetuses with increased nuchal translucency (NT) . Methods: Totally 101 cases out of 19 261 singleton fetuses who underwent the first trimester (11-13⁺⁶ weeks) ultrasound examination from January 2015 to June 2017 at First Affiliated Hospital of Sun Yat-sen University were diagnosed with NT ≥2.5 mm and underwent invasive prenatal test for fetal karyotype and CMA. According to the combination of other ultrasound abnormalities, the cases were divided into isolated group (67.3%, 68/101) and complicated group (32.7%, 33/101) . In addition, the cases were divided into 5 groups according to the thickness of NT, 2.5-2.9 mm (borderline thickening; 16.8%, 17/101) , 3.0-3.4 mm (33.7%, 34/101) , 3.5-4.4 mm (16.8%, 17/101) , 4.5-5.4 mm (15.8%, 16/101) , and ≥5.5 mm (16.8%, 17/101) . Chi square test was used to detect the different rates of other combined ultrasound abnormalities and abnormal chromosome between 5 groups. Results: The median thickness of NT was 3.4 mm (2.5-8.5 mm) . And 32 cases (31.7%, 32/101) had abnormal karyotype. There was a significant difference in the frequency of abnormal karyotype between the isolated and the complicated group (20.6% vs 54.5%, P<0.01) . Among 69 cases (68.3%, 69/101) of normal karyotype, 3 cases (4.3%, 3/69) were detected with pathogenic copy number variation (CNV) by CMA. Thirty-five cases with chromosomal abnormalities (include abnormal karyotype and pathogenic CNV) , there was a significant difference in the frequency of chromosomal abnormalities between the isolated and the complicated group (23.5% vs 57.6%, P=0.001) . The median age of pregnant women in 5 groups was 35 years (24-39 years) , 33 years (23-46 years) , 31 years (21-46 years) , 33 years (21-41 years) and 35 years (21-43 years) . The rates of chromosomal abnormalities increased with the increase of NT thickness. There was significant difference in the incidence of associated chromosomal abnormalities among 5 groups (P<0.05) . Comparative analysis within the 5 groups, the incidence of associated chromosomal abnormalities between NT 2.5-2.9 mm and ≥5.5 mm was significantly different (P=0.005) , while the differences between the other groups were not significant (P>0.05) . Conclusions: There is a high risk of fetal chromosomal abnormalities in borderline NT thickening (2.5-2.9 mm) at advanced maternal age, but the pathogenic CNV is not detected. Chromosomal microdeletion or microduplication could be further detected in the NT thickening (≥3.0 mm) fetuses with normal karyotype by chromosome microarray analysis, while the positive rate is relatively low, and the variants of unknown significance might be detected. 目的： 探讨染色体微阵列分析（CMA）技术检测颈部透明层（NT）增厚胎儿拷贝数变异（CNV）的临床价值。 方法： 2015年1月至2017年6月在中山大学附属第一医院行妊娠早期（11周~13周⁺⁶）超声筛查的胎儿共19 261例，其中超声提示NT≥2.5 mm且接受染色体核型分析及CMA检测的单胎胎儿101例（0.5%，101/19 261）。最终纳入研究的101例胎儿，（1）根据是否合并其他超声异常，分为单纯组68例（67.3%）和合并其他异常组33例（32.7%）；（2）根据NT值分为5组，2.5~2.9 mm组（即临界性增厚）17例（16.8%），3.0~3.4 mm组34例（33.7%），3.5~4.4 mm组17例（16.8%），4.5~5.4 mm组16例（15.8%），≥5.5 mm组17例（16.8%）。不同NT值组胎儿间合并其他超声异常及染色体异常的发生率比较采用χ²检验。 结果： （1）101例胎儿的中位NT值为3.4 mm（范围：2.5~8.5 mm）。（2）产前诊断结果：共32例（31.7%，32/101）胎儿的染色体核型异常，单纯组与合并异常组胎儿的染色体核型异常的发生率[分别为20.6%（14/68）、54.5%（18/33）]比较，差异有统计学意义（P<0.01）。69例（68.3%，69/101）染色体核型正常的胎儿中，CMA再检出3例（4.3%，3/69）含有致病性CNV，其NT值均>3.0 mm。染色体异常的35例胎儿中（包含核型异常及致病性CNV），16例（23.5%，16/68）为单纯组，19例（57.6%，19/33）为合并异常组，两组胎儿染色体异常的检出率比较，差异有统计学意义（P=0.001）。（3）不同NT值组胎儿：胎儿NT值为2.5~2.9 mm组、3.0~3.4 mm组、3.5~4.4 mm组、4.5~5.4 mm组、≥5.5 mm组孕妇的中位年龄分别为35岁（24~39岁）、33岁（23~46岁）、31岁（21~46岁）、33岁（21~41岁）、35岁（21~43岁）。随NT值的增加，胎儿合并染色体异常的发生率逐渐升高，5组胎儿染色体异常的检出率比较，差异有统计学意义（P<0.05）；两两比较，2.5~2.9 mm组与≥5.5 mm组胎儿染色体异常的发生率比较，差异有统计学意义（P=0.005），余组间比较，差异均无统计学意义（P均>0.05）。 结论： 母亲为高龄孕妇时，临界性NT增厚胎儿合并染色体核型异常的风险增高，但CMA未检出染色体核型正常的临界性NT增厚胎儿中的致病性CNV。CMA仅在染色体核型分析正常的NT增厚（NT≥3.0 mm）胎儿中可进一步检出染色体微缺失和（或）微重复，但检出率相对较低，同时也可检出临床意义不明的CNV。.

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