Concentration of growth hormone, prolactin and cortisol in fetal and maternal blood and amniotic fluid during late pregnancy and parturition in cows with cannulated fetuses

Abstract

Growth hormone, prolactin and cortisol concentrations were measured by radioimmunoassay in samples of fetal and maternal plasma and amniotic fluid from 15 days before until 24 hours after spontaneous parturition in cows. Average gestation length in ten cows with chronically catheterized fetuses was 267 ± 2.7 days (SEM). Mean fetal plasma GH concentrations decreased gradually during the last 15 days before birth ( r = 0.925, P < 0.01) and were 4–6 times higher than mean concentrations in maternal plasma. The latter did not change during the period under observation. GH and PRL concentrations in amniotic fluid were low during late gestation and showed no changes around parturition. Prolactin concentrations changed only in maternal plasma and reached peak values just before birth of the calf. The fetal cortisol concentration was significantly ( P < 0.05) elevated at Days −9 to −7 compared with that in samples taken before Day −9. A further increase occurred during the last week before birth. It is concluded that prepartum changes in the concentrations of GH, PRL and cortisol in fetal and maternal plasma and amniotic fluid are not synchronous but take place according to a pattern which is rather specific for each hormone in each of the compartments.