Changes in prostaglandin transfer across human fetal membranes obtained after spontaneous labor.

Increased prostaglandin E2 production from amnion is thought to be a critical step in the initiation of human parturition. However, it is not known whether amniotic prostaglandin E2 can reach the decidua and/or myometrium. We examined whether prostaglandin E2 could cross the amnion and full-thickness membranes and whether this capacity changed with active labor. Using an in vitro system we found that there was a time-dependent cumulative transfer of total radioactivity and of radioactivity corresponding chromatographically to prostaglandin E2 across amnion and full-thickness membranes. The rate of transfer across the amnion was faster than across full-thickness membranes and varied according to the site of tissue sampling within the uterus. The permeability constant for prostaglandin E2 transfer across full-thickness membranes was significantly higher in tissue collected after the spontaneous onset of labor than in tissue collected at elective cesarean section at term. We conclude that prostaglandin E2 produced in human amnion at term may escape metabolism in the chorion and reach the decidua and/or myometrium.