The effect of myometrial contractures on uterine blood flow in the pregnant sheep at 114 to 140 days' gestation measured by the 4-aminoantipyrine equilibrium diffusion technique.

Uterine blood flow, between 114 and 140 days' gestation, measured by the 4-aminoantipyrine equilibrium diffusion technique, was significantly decreased from 1359.1 +/- 84.4 ml X min-1 (mean +/- SE) in the absence of contractures to 1147.4 +/- 71.8 ml X min-1 (mean +/- SE) during a contracture (p less than 0.01). Contractures reduced total uterine blood flow regardless of whether the ewe was standing or lying. These observations are in keeping with the suggestion that changes in total uterine blood flow may be an important mechanism responsible for the previously described temporal relationship between contractures and fetal neurophysiologic function.