Correlations of maternal and fetal endocrine events with uterine pressure changes around parturition in the ewe.

In 4 Clun Forest ewes maternal peripheral plasma concentrations of progesterone were still elevated at the onset of parturient uterine activity. Fetal and maternal plasma concentrations of oestrogen started to rise before parturition and concentrations in maternal plasma were positively correlated with parturient uterine activity (P less than 0.05; r = +0.42). Fetal plasma concentrations of corticosteroids were positively correlated with fetal plasma concentrations of oestrogen (P less than 0.01; r = +0.65), but negatively correlated with maternal peripheral plasma progesterone concentrations (P less than 0.05; r = -0.50). Before parturition plasma concentrations of PGF rose but stayed high only in maternal peripheral plasma. Maternal peripheral plasma concentrations of PGF were positively correlated with uterine activity (P less than 0.05; r = +0.79) and plasma concentrations of oestrogen (P less than 0.05; r = +0.79), but negatively correlated with plasma concentrations of progesterone (P less than 0.01; r = -0.54).