Correlation of rate of uterine blood flow and plasma steroid concentrations at parturition in sheep

Abstract

Blood flow transducers were placed around 1 uterine artery per ewe and observations of the rate of blood flow through this artery and the peripheral plasma concentrations of free, unconjugated estrone, estradiol and progestagens were made at intervals of 1-3 days during the last 2-3 wk of pregnancy and at hourly intervals after spontaneous delivery at term. Rates of uterine blood flow decreased on average by 50% or more within the first hours of parturition and patterns of change in blood flow varied considerably among the animals. Spontaneous daily (pre partum) and hourly (post partum) changes in uterine blood flow were significantly correlated (P < 0.01) with the product of the concentrations of progestagens and of total free estrogens (estrone and estradiol) and with the product of progestagens and estradiol in peripheral blood.