Pathophysiology of increased nuchal translucency in chromosomally abnormalfetuses

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