Rate of fall in plasma progesterone and time to abortion following intra-amniotic injection of prostaglandin F2alpha, with or without urea, in the second trimester of human pregnancy.

Abstract

Progesterone concentrations have been determined in a total of 175 peripheral plasma samples obtained serially from 20 women undergoing mid-trimester abortion. In ten patients abortion was induced in intra-amniotic administration of 50 mg. of prostaglandin F2alpha (PGF 2alpha) alone; in ten others it was induced with 50 mg. of intra-amniotic PGF2alpha with 80 g. of urea. Mean instillation-abortion intervals were 29-0 hours in the group receiving PGF2alpha alone and 12-1 hours in the groups receiving PGF2alpha and urea. In eight of the patients treated with PGF2alpha and urea, and in four of those treated with PGF2alpha alone, there were significant decreases in progesterone level (determined by calculation of correlation coefficients) during the instillation-abortion iterval. When plotted against instillation-abortion times, calculated rates of decease in peripheral plasma progesterone levels showed a statistically significant regression (p smaller than 0-05). This indicates that progesterone levels drop most rapidly in patients with shorter instillation-abortion times. There was no relationship between initial progesterone levels and instillation-abortion times.