Does increased nuchal translucency indicate a fetal abnormality? A retrospective study to clarify the clinical significance of nuchal translucency in Japan

Abstract

The results of a chromosomal test by genetic amniocentesis in 58 cases with an increased nuchal translucency (NT; C3 mm thickness) revealed 47 cases showing a normal karyotype (81%) and 11 cases (19%) showing an abnormal karyotype. However, the cases of a normal karyotype with increased NT also included those with fetal abnormalities. Among the 49 cases in which NT was observed during the first trimester and then subsequently disappeared, chromosomal abnormalities were observed in five, and fetal abnormalities other than chromosomal abnormalities were observed in two. Meanwhile, all nine cases in which an increased NT remained or in which NT continued to increase in size during the second trimester were diagnosed as having cystic hygroma, and chromosomal abnormalities were found in six cases (67%). It should be noted that the shape of increased NT includes NT with a notch (notched NT) and NT without a notch (smooth NT). Among the 20 cases of notched NT, chromosomal abnormalities were observed in eight (40%), and cystic hygroma was observed in nine (45%). On the other hand, among the 38 cases of smooth NT, chromosomal abnormalities were observed in three (7.9%), but no cystic hygroma was observed. Our results confirm that increased NT does not always indicate a fetal abnormality. Whether NT thickness should be measured as a screening tool for fetal abnormalities remains controversial. However, increased NT may be detected by chance, because a maternal-fetal medical examination using ultrasonography is usually performed in Japan. It is therefore considered to be extremely important to establish a system in which cases are referred to obstetricians who are licensed clinical genetic specialists to obtain appropriate genetic counseling whenever increased NT is clinically observed.

Fetal nuchal edema and developmental anomalies caused by gene mutations in mice

“…Although increased NT is considered to be a transient physiological finding ( Yoshida et al, 2008 ), lymphatic dysfunction and heart defects described in this review are supposed to remain after birth. Even a subtle change in vascular permeability may put an impact on health during the long lifespan.…”

“…The causative genes have been identified in some but not many clinical cases of increased NT. Many cases of increased NT disappear during the second trimester and the majority of fetuses with increased NT are born normally ( Yoshida et al, 2008 ). Therefore, increased NT is considered to be a transient physiological finding, and the prognosis of fetal nuchal edema has not been sufficiently investigated.…”

A case report of Turner syndrome associated with fetal nuchal cystic hygroma and bilateral syndactyly of the hands and feet

“…Cystic hygroma is a macrocystic lymphatic malformation found in the posterior triangle between the neck and axilla in 75% of cases [2]. Cystic hygroma is regarded as an important marker for aneuploidy generally including trisomies but is a particularly common in Turner syndrome [3]. In fact the observation of cystic hygroma on ultrasound is attributable to Turner syndrome in 30–70% of cases [4].…”

Evolução perinatal e pediátrica de crianças com translucência nucal aumentada e cariótipo normal

“…Posteriormente, a medida da TN no primeiro trimestre da gestação passou a ser utilizada como método de rastreamento para cromossomopatias, podendo identificar cerca de 80% dos fetos acometidos para um falso positivo de 5% [6][7][8]11 . Quando utilizada juntamente com a idade materna e marcadores bioquímicos do primeiro trimestre, tem uma sensibilidade de 90%, passando a 95% quando acrescida da avaliação do osso próprio do nariz, para um falso positivo de 5% [12][13][14] .…”