Increased nuchal translucency may be related to a cystic hygroma or to mesenchymal edema. Increased nuchal translucency can be classified into three categories: 1) cardiac abnormalities, combined with abnormal ductus venosus flow velocities, is found, leading to the theory that cardiac failure causes nuchal translucency enlargement; 2) various types of abnormalities are found in the extracellular matrix of the nuchal skin of fetuses with increased nuchal translucency; 3) abnormal lymphatic development is demonstrated in fetuses with increased nuchal translucency.