Upon ultrasound examination, fetal cystic hygroma presents as a cystic mass with multiple septa with multiple, asymmetric, thin-walled cysts related to the posterior aspect of the neck. Cystic hygromas can range from increased nuchal translucency to thin-walled cystic masses that may become larger than the fetal head. The cysts may result from a lymphatic abnormality, possibly one caused by absent or inefficient connections between the lymphatic and venous systems. Depending on the site, the cut off may vary from site to site. Lowest would be 2.5 mm and highest 3.5 mm.