15-Keto-13,14-dihydroprostaglandin F2 alpha and prolactin in maternal and cord blood during prostaglandin E2 or oxytocin therapy for labor induction.

15-keto-13,14-dihydroprostaglandin F2 alpha plasma levels were measured in pregnant women following labor induction with either oral PGE2 treatment or intravenous oxytocin, both combined with amniotomy. The median time to start of contractions was 62 minutes in the PGE2 treated group and 45 minutes in the oxytocin treated group (p less than 0.01; median test). The increase in 15-ketodihydro-PGF2 alpha appeared earlier in the PGE2 group but not in the oxytocin group (p less than 0.001 and p = 0.210, respectively). At delivery, the 15-ketodihydro-PGF2 alpha values had further increased in both treatment groups. The increase was significantly higher in the PGE2 treated patients compared with oxytocin treated patients (p = 0.03; contrast test). Despite higher 15-ketodihydro-PGF2 alpha concentrations throughout parturition, PGE2 women did not deliver more rapidly than oxytocin infused women. There was no correlation between 15-ketodihydro-PGF2 alpha blood concentrations and either onset of contractions or labor time. The decrease in maternal serum prolactin concentration during parturition was pronounced (p less than 0.001) in the PGE2 group but occurred also in oxytocin treated patients (p less than 0.02). A single oral dose (0.5 mg) of PGE2 taken by non-pregnant women led to significant (p less than 0.05) increases in 15-ketodihydro-PGF2 alpha levels in blood plasma after 10 minutes. This increase persisted for at least 90 minutes. It is suggested that oral PGE2 may be transformed into PGF2 alpha and/or induce endogenous PGF2 alpha biosynthesis.