The placental and fetal response to the intra-amniotic injection of prostaglandin F2alpha in midtrimester abortions.

The placental and fetal response to the intra-amniotic injection of prostaglandin F2alpha (PGF2alpha) for midtrimester abortions was evaluated. Maternal blood samples for radioimmunological determinations of serum progesterone, human placental lactogen (HPL) and alpha-fetoprotein (AFP) were taken before and serially until 24 hours after the injection of 40 mg (nine patients) or 75 mg (seven patients) of PGF2alpha. Fetal heart action was monitored ultrasonically during the same period. The average induction-abortion interval was 22-6 hours and was indepedent of the dose of PGF2alpha used. The mean progesterone and HPL levels showed a significant fall half an hour after PGF2alpha. The constant decreases began only at 5 hours and later. The mean AFP levels increased rapidly after 5 hours following injection of PGF2alpha. The feral heart stopped at a mean of 10-4 hours (range 0-5 to 25 hours) after the injection of PGF2alpha. No relationship between the time of fetal death or rises in AFP and the induction-abortion interval could be detected. The primary hormonal response of the placenta and the efficacy of exogenous PGF2alpha were not related, indicating the possibility that the abortifacient property of PGF2alpha is not related to its primary effect on placental hormone synthesis or release.