The clinical impact of the first trimester nuchal translucency between the 95^th‐99^th percentile

Objectives To evaluate the clinical significance of nuchal translucency (NT) between the 95th-99th percentile, in terms of typical and atypical chromosomal abnormalities (ACA), associated fetal congenital defects and postnatal outcome. Methods Retrospective cohort study of fetuses with NT between the 95th-99th percentile. Data regarding rate of associated fetal defects, genetic abnormalities and postnatal outcome were collected. Results A total number of 306 cases of fetuses with a NT between the 95th-99th percentile 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 ACA 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). Conclusions The presence of a NT between the 95th-99th percentile 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. This article is protected by copyright. All rights reserved.