Umbilical cord is the major source of prostaglandin E2 in the gestational sac during term labor

The umbilical cord is an amniotic structure histologically resembling amnion lining the basal plate and reflected chorion. Prostaglandin E2 is secreted by amnion and is present in amniotic fluid. This study measured prostaglandin E2 production by amnion from all three locations to determine the relative contributions of prostaglandin E2 to amniotic fluid at term. Total surface areas and weights of umbilical cord, basal placental plate, and reflected chorionic amnion were measured in afterbirths from 20 normal patients delivered at term by elective repeat cesarean section before the onset of labor or vaginally after spontaneous onset of labor. Subsequently, 2 cm lengths of umbilical cord and 8 cm2 disks of basal placental plate and reflected chorionic amnion were incubated in perfusion chambers, and prostaglandin E2 production was measured by radioimmunoassay. Umbilical cord accounted for the least surface area (16% to 17%) but greatest tissue mass (75% to 76%). Both basal placental plate and reflected chorionic amnion increased prostaglandin E2 production 2.3-fold and 4.1-fold, respectively, after labor versus before labor, whereas umbilical cord prostaglandin E2 output was unchanged. However, umbilical cord accounted for 66% and 44% of the total prostaglandin E2 output before labor (697 +/- 169 ng/hr) versus (1201 +/- 380 ng/hr) after labor. Thus, of the three amniotic locations, umbilical cord represents the principal site of prostaglandin E2 production within the gestational sac.