Cervical ribs: Useful marker of monosomy X in fetal hydrops

Cervical ribs were observed in six hydropic fetuses with 45X karyotype. To test the usefulness of this observation in the macerated hydropic fetus whe re chromosome culture is problematic, a group of 36 hydropic fetuses was ex amined. Cases were chosen to include fetuses with several karyotypic and pa thological abnormalities known to be associated with fetal hydrops. Whole-b ody anteroposterior radiographs were evaluated without Knowledge of the fet al karyotype or pathological findings. Twenty-five fetuses had an abnormal karyotype, seven had a normal karyotype and in four culture failed. In the last group, the number of X, 21 and 18 chromosomes per nucleus was estimate d using FISH. Radiographic analysis demonstrated that among the 16 fetuses with 45,X karyotype or a single copy of X and female phenotype, 12 had a pa ir of cervical ribs. Three other fetuses had a single cervical rib. Only on e fetus had no cervical ribs. The last fetus had tubular hypoplasia of the aortic arch and persistent mesocolon. Twelve of the sixteen 45,X fetuses ha d tubular hypoplasia of the aortic arch. Seven had other cardiovascular ano malies, five had renal anomalies, and five had anomalies of intestinal rota tion. Cervical rib appears to be more common than other frequently recorded associations of 45,X. It is a useful and easily demonstrated mark in the e valuation of the macerated hydropic fetus.