The clinical impact of the first-trimester nuchal translucency between the 95th-99th percentiles

ObjectivesTo evaluate the clinical significance of nuchal translucency (NT) between the 95th-99th percentile in terms of typical and atypical chromosomal abnormalities (ACAs), associated fetal congenital defects and postnatal outcome. MethodsA retrospective cohort study of fetuses with NT between the 95th-99th percentile. Data regarding the rate of associated fetal defects, genetic abnormalities and postnatal outcome were collected. ResultsA total of 306 cases of fetuses with an NT between the 95th-99th percentiles were included. The overall rate of genetic abnormalities was 12.1% (37/306). Chromosomal abnormalities were found in 10.1% (31/306) of cases and 2% were ACA (6/306). Within this group, two were pathogenic Copy Number Variants (CNVs) and four were single gene disorders. The overall rate of fetal congenital defects was 13.7% (42/306). All ACAs were found in fetuses with congenital defects. Postnatally, a new diagnosis of a single gene disorder was made in 0.85% of cases (2/236). ConclusionsThe presence of an NT between the 95th-99th percentiles carries a 10-fold increased risk of fetal defects, representing an indication for referral for a detailed fetal anatomy evaluation. The risk of ACA is mainly related to the presence of fetal defects, irrespective of the combined test risk.

Automated summary

This study evaluates the clinical significance of nuchal translucency (NT) between the 95th-99th percentile in terms of typical and atypical chromosomal abnormalities (ACAs), associated fetal congenital defects, and postnatal outcomes. It found that an NT between the 95th-99th percentiles is associated with a 10-fold increased risk of fetal defects and a 12.1% rate of genetic abnormalities. This suggests the need for a detailed fetal anatomy evaluation for these cases.