Analysis of copy number variation by CMA in fetus with increased nuchal translucency

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 0.05) . 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. Key words: Nuchal translucency measurement; Ultrasonography, prenatal; Microarray analysis; DNA copy number variations