The effects of combined dexamethasone and indomethacin treatment on the outcome of pregnancy in the rabbit.

Abstract

Pregnant rabbits were treated with dexamethasone, 6 mg/day i.m. from Day 21 until delivery, dexamethasone alone induced premature parturition (27.0 ± 0.6 S.D. days, P<0.001). These results confirm previous studies. In addition, the delay in parturition caused by indomethacin was found to be associated with a delay in the preparturient decline in plasma progesterone (treated higher than untreated on Day 30, P<0.05), supporting the view that prostaglandin-induced luteolysis plays a role in the physiologic termination of pregnancy. The results obtained with the animals which were treated with both dexamethasone and indomethacin were not different from those observed with dexamethasone treatment alone. There was no delay of the dexamethasone-induced decline of plasma progesterone or of the premature parturition (26.3 ± 2.5 S.D. days). These results and previous observations suggest that the suppression of plasma progesterone and the induction of parturition by dexamethasone in this species may differ from spontaneous parturition in regard to the role of prostaglandin synthesis in causing the fall in plasma progesterone.