Prenatal diagnosis of a posterior nuchal cystic hygroma was made at 13 weeks of gestation in a fetus diagnosed at birth with Noonan syndrome. Through serial sonographic evaluation during pregnancy, the embryologic evolution of cystic hygroma into nuchal skin thickening was appreciated and later correlated with postnatal findings of nuchal skin fold redundancy and pterygium colli in a patient with Noonan syndrome. These observations support the concept of the jugular lymphatic disruption sequence as pathogenesis of the nuchal findings in severely affected Noonan syndrome patients.