Cortisol levels in amniotic fluid in prostaglandin F2alpha-induced midtrimester abortion

Cortisol concentrations in amniotic fluid and maternal plasma were determined by a competitive protein-binding assay in 14 patients in the midtrimester of pregnancy before and after intra-amniotic administration of prostaglandin F2alpha. Samples were obtained at three-hour intervals until abortion or until the fetal heartbeat ceased. The mean plasma levels of cortisol increased from 324 +/- 173 ng. per milliliter at hour 0 to 524 +/- 272 ng. per milliliter at 6 hours (the peak elevated value). In amniotic fluid, the mean levels of cortisol increased from 4.71 +/- 2.5 ng. per milliliter to a maximum at 9 hours of 10.24 +/- 2.5 ng. per milliliter. We concluded that at 16 to 20 weeks' gestation the fetoplacental unit is capable of responding to prostaglandin F2alpha instillation by increased levels of cortisol in the amniotic fluid.