Time-trend analysis of plasma 11-desoxycorticosterone, corticosterone, cortisol, and aldosterone in fetal and maternal sheep during the last 18 days of gestation

We examined the time trend effects of approaching parturition on fetal and maternal concentrations of cortisol, corticosterone, 11-desoxycorticosterone and aldosterone in eight chronically catheterized pregnant sheep preparations. Fetal plasma cortisol describes a continuously incrementing, straight log-linear function from at least 18 days prior to delivery. Fetal plasma corticosterone describes a time trend effect similar to that of fetal plasma cortisol. Fetal plasma 11-desoxycorticosterone shows no overall time trend effect except for a terminal rise beginning at approximately delivery — 2 days. Maternal plasma cortisol, corticosterone, and 11-desoxycorticosterone concentrations show no overall time trend effects except for similar terminal rises beginning at approximately delivery — 3 days. Both fetal and maternal plasma aldosterone concentrations show wide random fluctuations with no discernible time trend effects. Concentrations of fetal and maternal 11-desoxycorticosterone and aldosterone respectively do not correlate with one another ( P > 0.05) or with cortisol and corticosterone ( P > 0.10) and must therefore be regulated through different control mechanisms. Maternal cortisol, corticosterone, 11-desoxycorticosterone and aldosterone concentrations bear no apparent relationship over time to their fetal counterparts with the approach of parturition.