Chromosomal microarray in fetuses with increased nuchal translucency

To assess the clinical value of using high-resolution chromosomal microarray (CMA) for the examination of genomic imbalances in prenatal uncultured chorionic villus samples from fetuses with increased nuchal translucency (NT) and a normal quantitative fluorescent polymerase chain reaction (QF-PCR) result, in a clinical setting in which more than 95% of pregnant women receive first-trimester combined screening.

From January 2013 to July 2014, we included 132 chorionic villus samples from consecutive ongoing pregnancies, with fetal NT ≥ 3.5  mm at 11-13 weeks' gestation, from obstetric units (publicly funded healthcare) in Central and North Denmark Regions. DNA was extracted directly from the samples and examined with QF-PCR (n = 132) and 180 kb oligonucleotide array-based comparative genomic hybridization (n =  94).

In 38 cases, aneuploidies for chromosomes 18, 21 or X, or triploidy, were detected by QF-PCR. Among the 94 cases with a normal QF-PCR result, we detected pathogenic copy number variants (CNVs) by CMA in 12 fetuses (12.8% (95% CI, 7.5-21.0%)). In an additional three (3.2%) cases, CNVs with uncertain clinical significance were detected.

CMA is a valuable diagnostic technique in pregnancies with isolated fetal NT ≥ 3.5 mm.