[Application of chromosomal microarray analysis in prenatal diagnosis of fetuses with increased nuchal translucency]

To determine the frequency of chromosomal abnormalities and outcome of pregnancy for fetuses with increased nuchal translucency (NT).

Between July 2014 and February 2018, 247 fetuses with increased NT (>95th centile)were analyzed by chromosome microarray analysis (CMA). The fetuses were divided into ones with isolated increased NT (168 cases), increased NT with cystic hygroma (20 cases), increased NT with edema (12 cases) or increased NT with other abnormalities (47 cases). All couples were followed up by telephone calls.

The rate of chromosomal abnormalities was 31.6% (78/247), which included 66 cases with chromosomal aneuploidies and 12 with copy number variants (CNVs). CNVs accounted for 31.4% (11/35) of total abnormalities among fetuses with isolated increased NT, whilst only 2.3% (1/43) of the total abnormalities among fetuses with non-isolated increased NT. Three fetuses with a normal CMA result had mental and physical retardation. Two of them were diagnosed with single gene disorders by whole exome sequencing.

CMA can detect more chromosomal microdeletion/microduplications among fetuses with isolated increased NT. Furthermore, fetuses with increased NT and anegative CMA result during pregnancy cannot exclude all adverse outcomes.