Effects of exogenous progesterone and estrone on conceptus development in swine

Administration of progesterone (P4, .55 mg/kg) and estrone (E1, .275 micrograms/kg) during discrete periods in early gestation was found to have beneficial effects on conceptus development in gilts. Three trials were conducted, with each trial examining two hormone treatment groups and one control group. In all trials, P4-E1 supplementation for either one or both of the time periods examined resulted in larger (P less than .05) placentas at d 50 of gestation. Administration of exogenous P4-E1 from either d 20 to 30 (trial 1) or d 25 to 30 (trial 3) of gestation resulted in the greatest augmentation in placental development. In all three trials, exogenous P4-E1 elicited beneficial effects on areolae formation and development. In all nine groups examined (both P4-E1-treated and controls), a positive uterine artery minus uterine vein difference in progesterone concentration was found. This suggests that the conceptus is metabolizing progesterone to metabolites that may have a local effect within the pregnant uterus. It is suggested that augmentation of placental growth, as demonstrated in this study, may reduce secondary fetal death losses in latter gestation (i.e., post-d 70) due to placental insufficiency.