[Increased nuchal translucency pathophysiology]

Increased physiological nuchal translucency (NT) between 10 and 14 weeks of gestation is associated with chromosomal anomalies, mainly trisomy 21, developmental malformations and with normal fetus outcome. The aim of this study is to understand the cellular mechanisms leading to increased NT.

We examined five nuchal samples, a normal fetus from a fetal loss with a normal NT, a trisomy 21 fetus with an increased NT, two karyotypically normal fetuses with increased NT and a fetus with increased NT associated with an isolated cardiopathy. These morphological data were correlated with data from the literature.

The pathological mechanism of increased NT is a posterior median mesenchymal edema of the fetal neck. It is associated with bilateral distension of jugular lymphatic vessels.

Increased NT mechanisms are mainly related to a disturbance of embryonic lymphangiogenesis which might be a common denominator of the alteration of the composition of the extracellular matrix and of the cardiovascular and hemodynamic disorder. Nuchal morphological studies should be systematically performed to understand the mechanisms of increased NT.