Chorioamniotic membrane separation: a potentially lethal finding.

Sonographic detection of chorioamniotic membrane separation (CMS) has been considered a benign incidental finding. We now report 6 cases of CMS identified by prenatal ultrasound; 1 in an otherwise normal pregnancy and 5 following fetal surgery. Following membrane separation, amniotic bands formed and compromised the umbilical cord in 4 cases leading to 2 fetal deaths. In the first case, CMS was detected by ultrasound at 22 weeks' gestation in an otherwise uncomplicated pregnancy. Because CMS was considered benign and umbilical cord blood flow was ample, the mother was followed by intermittent sonographic examinations. Fetal demise occurred 2 weeks later, clearly due to umbilical cord strangulation by an amniotic band. Surprised by this unexpected outcome, we reviewed our experience with CMS after hysterotomy for fetal surgery. Out of more than 40 fetal surgical cases, we have 5 cases in which CMS was recognized after hysterotomy. Three of these fetuses had umbilical cord compromise by a band of amniotic membrane leading to 1 fetal death. This experience demonstrates that membrane separation may be associated with amniotic band formation which can lead to cord strangulation and fetal compromise. Following fetal surgery, serial ultrasound evaluation and close fetal monitoring are indicated. In otherwise unremarkable pregnancies, clinician awareness of the possibility of amniotic band formation following CMS should be heightened. In either situation, knowledge of this potential life-threatening complication may identify cases in which cord compromise requires emergent delivery or fetoscopic release of the strangulating amniotic band.