[Alterations of oxytocin and prostaglandin E1, E2, F2 alpha levels in human plasma during labor (author's transl)].

In order to investigate the role of oxytocin (OT) and prostaglandins (PGs) in the mechanism of labor onset, changes of OT and PGs levels in human plasma were evaluated before labor, soon after the labor onset, and at the time of established labor in the following three groups. Group 1 consisted of 6 cases with spontaneous labor, group 2, of 6 cases with induced labor with PGF2 alpha drip infusion, and group 3, of 5 cases with induced with PGE2 vaginal suppository. OT concentrations were measured by RIA, PGE1, PGE2, and PGF2 alpha were extracted and determined by Inagawa's method. Levels of OT in group 1 were divided into two subgroups: subgroup 1 with high OT levels (24.0-116.2 microunits/ml) and subgroup 2 with low OT levels (below 7.2 microunits/ml) throughout labor. Changes of PGs level in subgroup 1 showed no definite tendency during labor, suggesting that OT appears to play the leading role in spontaneous labor. Those in subgroup 2 showed a particular behavioral pattern during labor, suggesting an important role played by PGs for the onset of labor following rupture of the membranes. The results of groups 2 and 3 are fully discussed in terms of labor process.