Pregnancy was terminated with prostaglandin E2 in 65 women harboring a dead fetus for 3 days to 8 weeks. The study was designed to: (1) elucidate the mechanism of failed onset of labor in the presence of fetal death, (2) determine appropriate dose-response relationships, and (3) evaluate safety and efficacy of this new method of intervention. Results indicate that plasma progesterone levels from 12 to 40 weeks' gestation are in the lower normal statistical range as compared to those seen in pregnancy with a living fetus. Uterine size as estimated from fetal birth weight is also in the low normal range compared to that seen in a viable pregnancy. Hence the uterine volume-progesterone ratio is equal to or greater than that in normal pregnancy and thereby partially explanatory for the failed initiation of labor. The dosage required to produce delivery declined in each month's grouping from a mean of 56 +/- 26 (SD) mg at 12 to 15 weeks to 22 +/- 8.4 mg at 38 to 40 weeks. Dose-delivery response did not correlate with age, parity, or progesterone levels but did correlate with oxytocin response. Three unusual and serious complications occured.