A case report of complete chorioamniotic membrane separation.

We describe a patient with complete chorioamniotic membrane separation (CMS). During embryologic development, the chorionic and amniotic membranes each arise from their own germ layers and form a celomic cavity in the first trimester of pregnancy. By the early second trimester, the cavity has shrunk and the membranes become conjugated. However, the membranes may separate spontaneously or because of an invasive intrauterine procedure. This pathologic condition is referred to as CMS. Extensive CMS can lead to miscarriage, fetal death, neonatal death, amniotic band syndrome, umbilical cord complications, and preterm delivery. In this case, CMS was detected in the 29th week of pregnancy with a routine ultrasonographic examination in the absence of a distinct non-reassuring fetal status or an abnormality of the intrauterine environment. The patient had undergone amniocentesis at 16 weeks of pregnancy for chromosomal analysis. Ultrasonography showed a floating membranous structure in almost every view of the intra-amniotic cavity. Thus, complete CMS was believed to have occurred. Therefore, precautionary checkups and examinations were periodically performed. Childbirth took place uneventfully by means of elective cesarean section in the 37th week of pregnancy. Because pathological examination showed complete CMS, the validity of the prenatal diagnosis was confirmed.