A study of the effect of mifepristone (antiprogesterone) followed by prostaglandin on uterine activity and fetal heart rate in patients having a termination of pregnancy.

In the 72 h after a single oral dose of 400 mg of the antiprogesterone mifepristone, 12 out of 14 first and one second trimester fetuses had a slight increase in heart rate; 2 fetuses died and one aborted. During the same 72 h, uterine activity increased moderately, and was physiological with no increase in resting pressure. The treatment sensitized the uterus to prostaglandin (PG) about ten-fold. A low, 0.05 mg IM, dose of sulprostone caused the demise of 5 more fetuses and caused the onset of clinical abortion in less than 2 h. After a relatively short hypertonic phase uterine resting pressure fell to normal levels and active contractions occurred leading to expulsion of uterine contents. The plasma level of progesterone (P) remained unaltered after mifepristone treatment, but the levels of estradiol 17b (E2) and cortisol increased. The plasma level of mifepristone was 1640 +/- 424 ng. ml -1 at 72 h, and the substance was still detectable after one week.