Pathophysiology of increased nuchal translucency in chromosomally abnormal fetuses

In about 70% of fetuses with trisomies 21, 18 or 13 or Turner syndrome, there is increased collection of fluid in the neck region that can be visualized sonographically at. 11-14 weeks of gestation as increased nuchal translucency thickness; Increased nuchal translucency is also observed in a high proportion of fetuses with cardiac defects, and a wide range of other major structural abnormalities and genetic syndromes. The heterogeneity in conditions associated with increased nuchal translucency suggests that there may not be a single underlying mechanism for the fluid collection in the skin of the fetal neck. Possible mechanisms include cardiac failure in association with abnormalities of the heart and great arteries, abnormal or delayed development of the lymphatic system, altered composition of the subcutaneous connective tissue, and venous congestion in the head and neck in association with superior mediastinal compression. This article reviews the studies using ultrastructural and molecular biology techniques to investigate the pathophysiology of increased nuchal translucency.