The prenatal sonographic features of Noonan's syndrome.

The sonographic findings in four infants with Noonan's syndrome are described. All four fetuses had cystic hygromata located laterally along the cervical spine and normal karyotypes. Three of the four pregnancies were complicated by polyhydramnios and those three fetuses had associated pleural effusions. One fetus developed frank hydrops and did not survive, a clinical course that appears to be part of the clinical spectrum of Noonan's syndrome. The diagnosis of Noonan's syndrome was given serious consideration prenatally based on the sonographic findings and normal karyotype and confirmed at birth in all four cases. Three of the infants survived.