Pathophysiology of increased nuchal translucency in chromosomally abnormalfetuses

In about 80% of fetuses with trisomies 21, 18 or 13 and Turner syndrome the re is an increased collection of fluid in the neck region that can be visua lized sonographically at 10-14 weeks gestation as increased nuchal transluc ency thickness. The pathophysiology of this common phenotypic expression of different chromosomal abnormalities is uncertain, but there is some eviden ce that the underlying mechanism may be cardiac failure, possibly due to ab normalities of the heart and great arteries, and altered composition of the extracellular matrix of tissues, which can be also noticed in the skin. Th e latter may be due to a gene dosage effect of the three rather than the no rmal two copies of genes found in trisomies, causing an alteration of the e xtracellular matrix in the skin or abnormal development of the heart and gr eat arteries.