INCREASE IN PROSTAGLANDIN BIOAVAILABILITY PRECEDES THE ONSET OF HUMANPARTURITION

The traditional paradigm that prostaglandins (PGs) are of central impo rtance in the initiation of labor has been challenged. A group of inve stigators has recently reported that the amniotic fluid concentrations of PGE(2) and PGF(2 alpha) increase only late in the course of labor implying that 'the accumulation of prostaglandins in amniotic fluid is an after-effect of labor and not indicative of a role of these compou nds in the initiation of human parturition'. The present study was con ducted to determine whether amniotic fluid prostaglandin concentration s increase prior to the onset of human labor, the central question in this controversy. Three amniocenteses were performed in 17 women with intrahepatic cholestasis of pregnancy - the first two prior to the ons et of labor and the third during early spontaneous labor. PGE(2) and P GF(2 alpha) were measured with sensitive and specific radioimmunoassay s. Amniotic fluid concentrations of PGE(2) and PGF(2 alpha) increased prior to the onset of spontaneous labor. An additional increase in the concentrations of PGE(2) and PGF(2 alpha) was found in samples obtain ed in early labor. We conclude that an increase in prostaglandin bioav ailability precedes the onset of spontaneous human parturition.