[Differential diagnostic procedure in sonographically detected fetal cystic hygroma]

A series of 5 consecutive cases of fetal cystic hygroma diagnosed prenatally in the second trimester by sonography within a year in an ultrasound screening program is presented. 3 fetuses had a 45,X karyotype, one fetus had a 47,XY,+21 chromosome constitution and in one case no cytogenetic abnormality could be found. Because there was a cleft palate present in this latter female fetus, it is possible that this was a case of the recently described malformation syndrome. 3 of the pregnancies with fetal cystic hygroma ended in spontaneous abortion, in the other 2 cases the parents decided after careful genetic counseling to have an elective termination of pregnancy. Although Turner syndrome is the most frequent finding in cases of nuchal hygroma detected in utero by ultrasound, careful sonographic and cytogenetic studies as well as a detailed family history have to be obtained to delineate the cause of the malformation. On autopsy in all 3 cases with 45,X karyotype there were streak gonads, in 2 cases an additional hypoplasia of the aortic arch was found. Amniotic fluid alpha-fetoprotein and acetylcholinesterase determinations did not prove to add any significant information to the ultrasound evaluation of fetal cystic hygroma.