Prolapsing amniotic membranes: detection, sonographic appearance, and management.

Seventeen cases of prolapse of the amniotic membranes through a partially dilated endocervical canal are presented. Most of the patients had no prior history of incompetent cervix and less than half had either a therapeutic or spontaneous abortion. The prolapsed amniotic membranes are accompanied by uterine contractions and usually occur in the late second or early third trimester of pregnancy. Ultrasound was useful in confirming clinical findings, defining the extent of the prolapsed amniotic membranes, determining fetal viability, and demonstrating contents of the amniotic membranes. Tocolytics, abdominal amniocentesis, and cervical cerclage were of little benefit in preventing immediate delivery. Of the 17 patients, ten were live births and eight were stillbirths or immediate death due to prematurity.