Reexamining the optimal nuchal translucency cutoff for diagnostic testing in the cell-free DNA and microarray era: results from the Victorian Perinatal Record Linkage study

The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine recently recommended offering genetic counseling and diagnostic testing for enlarged nuchal translucency at ≥3.0 mm, regardless of previous negative screening with noninvasive prenatal testing. This study aimed to perform a population-based, individual record linkage study to determine the optimal definition of an enlarged nuchal translucency for the detection of atypical chromosome abnormalities. This was a retrospective study of women resident in Victoria, Australia, undergoing combined first-trimester screening during the 24-month period from January 2015 to December 2016. Linkages between statewide results for combined first-trimester screening, prenatal diagnostic procedures, and postnatal cytogenetic results from products of conception and infants up to 12 months of age were used to ascertain the frequency and type of chromosome abnormality by gestation and nuchal translucency measurement. An atypical chromosome abnormality was defined as any major chromosome abnormality other than whole chromosome aneuploidy involving chromosomes 21, 18, 13, X, and Y. Of the 81,244 singleton pregnancies undergoing combined first-trimester screening, 491 (0.60%) had a nuchal translucency of ≥3.5 mm, 534 (0.66%) had a nuchal translucency of 3.0 to 3.4 mm, and 80,219 (98.74%) had a nuchal translucency of < 3.0 mm. When grouped by nuchal translucency multiples of the median (MoM), 192 (0.24%) had a nuchal translucency of ≥3.0 MoM, 513 (0.63%) had a nuchal translucency of 1.9 to 2.9 MoM, and 80,539 (99.13%) had a nuchal translucency of