Introduction
Nuchal translucency (NT) is a subcutaneous fluid collection behind fetal
neck and it is physiologically present in the first trimester in all
fetuses1. In the early ’90, Nicolaides introduced NT
measurement as part of first trimester screening for trisomies 21, 13
and 182 and over the years an increased NT has been
associated with several pathological conditions such as adverse
pregnancy outcome3-4, chromosomal abnormalities other
than common trisomies, genetic syndromes5-9, and
structural anomalies3;8, in particular cardiac
malformations10-11. Therefore, pregnancies with an
increased NT are considered at high risk and detailed fetal ultrasound,
fetal echocardiography, genetic counselling and chorionic villous
sampling (CVS)/amniocentesis are usually offered to these patients.
Reference ranges and percentiles for NT based on gestational age have
been established in a large study by Snijders et
al.12. International guidelines, however, do not show
complete agreement regarding the cut off of NT value or percentile that
requires further investigations; the most commonly used are either 3.5
mm, 3 mm or the 99th percentile13-17(Table 1). Usually, cases of NT between the
95th-99th percentile are managed as
healthy pregnancies.
Recently, the accuracy of ultrasonographic technology has markedly
increased and new genetic tests such as CGH-array (Comparative Genomic
Hybridization) and exome sequencing, have been introduced in clinical
practice, allowing to be more accurate in the diagnosis of fetal
anomalies, chromosomal abnormalities and genetic syndromes.
The aim of our multicentric study was to evaluate all women with NT
between 95th and 99th percentile and
discuss a possible new cut off for fetal and genetic tools usually
provided to higher cut offs.