Maternal steroid changes after fetal death until delivery of the dead sheep fetus

Progesterone, estrone, and estradiol have been determined during late pregnancy and at parturition in the maternal plasma of sheep bearing live and dead fetuses. Mean concentrations of the steroids at days 125--130 after mating were lower after fetal death, although the differences were not significant. The mean interval between fetal death and delivery was 11.8 +/- 5.8 (0.01 +/- 0.01 ng/mL) on the day of delivery. There was no preparturient rise in maternal estrogen levels in animals with dead fetuses. The ratios of progesterone:estradiol and progesterone:estrone fell from 130 and 140 to 2.9 and 1.2, respectively, during the 5 days prior to delivery due entirely to the fall in progesterone. In normal animals the ratios of progesterone:estradiol and progesterone:estrone decreased from 186.1 and 81.7 at 5 days before parturition to 9.4 and 2.0 on the day of birth. This was attributable partly to a fall in progesterone but largely to the preparturient rise in estrone and estradiol. We conclude that some placental steroid output continues after fetal death in the sheep but that deliveries of both dead and live fetuses are associated with an abrupt change in the ratio of progesterone:estrogens in maternal blood.