Separated chorioamnion and elevated chorion: sonographic features and clinical significance.

The clinical presentation and outcome of pregnancy was analyzed in thirteen patients in whom a free-floating intrauterine membrane was found on sonography. The cases were divided into two groups: those with elevated chorion and those with chorioamniotic separation. Five of seven patients with chorioamniotic separation progressed normally to term and delivered normal infants. In the two pregnancies with chorioamniotic separation that did not progress to term, one was associated with a placental chorioangioma and the other had a dead fetus that had a cystic hygroma indicative of Turner's syndrome. Of the six patients with elevated chorion, all presented with an episode of vaginal bleeding in the early second trimester. Five of six patients with elevated chorion progressed to term with the delivery of normal infants. One patient with extensive elevation of the chorion aborted. Three patients with elevated chorion had a subchorionic clot, whereas this was not present in patients with separated chorioamnion. Follow-up sonographic examination of patients with separated chorioamnion and elevated chorion revealed that most (11 of 13), but not all pregnancies in which an intrauterine membrane was found progressed to term without complications.