Ovine placental lactogen concentrations during premature delivery induced by infusion of dexamethasone or adrenocorticotrophin to the fetus.

Premature delivery was induced by intrafetal infusion of dexamethasone or (1-24)ACTH, starting between days 124 and 129 of pregnancy in twelve ewes carrying intact (n = 7) or hypophysectomized (n = 5) single fetuses. Concentrations of ovine placental lactogen (oPL) in maternal plasma were measured by specific radioimmunoassay before and during premature delivery. There was no significant change in oPL concentrations before delivery in ewes carrying either intact or hypophysectomized fetuses. The results suggest that a prepartum decline in oPL is not an essential prerequisite for delivery, and indicate that fetal glucocorticoids are not directly responsible for the prepartum fall in oPL concentrations observed at spontaneous delivery.