For a study, researchers sought to determine the possibility of clinically meaningful chromosomal microarray analysis results in fetuses with nuchal translucency of 3.0–3.4 mm. In addition, they wanted to know how effective noninvasive prenatal testing (NIPT) was in these pregnancies. The findings of all chromosomal microarray analysis tests done due to a nuchal translucency measurement of 3.0–3.4 mm, without ultrasonographic abnormalities, were collected for this retrospective cohort research. The prevalence of clinically relevant (pathogenic and possibly pathogenic) microarray results was compared to a previously reported local control group of 2,752 fetuses with normal ultrasonography findings and nuchal translucency less than 3.0 mm.

Because of isolated nuchal translucency ranging from 3.0–3.4 mm, 619 chromosomal microarray studies were done in total. About 29 (4.7%) of these instances exhibited clinically significant copy number variations, putting them at a considerably greater risk than control-group pregnancies (relative risk 3.3, 95% CI 2.6–7.2). Except for the subgroup of 198 fetuses with nuchal translucency measures of 3.0 mm, the risk for aberrant chromosomal microarray analysis findings remained considerably higher when divided by tenths of millimeters. Noninvasive prenatal testing for the five most prevalent chromosomal aneuploidies would have missed 41.4% of the aberrant copy number variants—1.9% of all cases, or 1 in 52 fetuses with nuchal translucency between 3 and 3.4 mm. Traditional karyotyping and genome-wide NIPT might have missed an aberrant result in 9 of 619 (1.5%), or 1 in 69 pregnancies. 

The data revealed that in pregnancies with nuchal translucency of 3.1–3.4 mm, the rate of aberrant chromosomal microarray analysis findings was considerably greater than in fetuses with normal ultrasound findings.