Uterine Blood Flow and Plasma Norepinephrine Changes during Maternal Stress in the Pregnant Ewe

Abstract

Because maternal stress may adversely affect the fetus, effects of brief episodes (15-60 s) of maternal stress in 18 awake pregnant ewes was tested. Maternal agitation and struggling occurred either after non-painful stimuli, e.g., loud noises or sudden movements of personnel (10 animals), or after the brief application to the ewe''s skin of a uniform electrical stimulus of 30 V with a frequency of 167 Hz for 30-60 s (8 animals). Stimulation of either type produced a 45-50% increase in mean arterial blood pressure and a concomitant 32-52% decrease in uterine blood flow (P < 0.05). The decreases in uterine blood flow were brief, lasting less than 3 min, and were not associated with fetal asphyxia. Maternal plasma norepinephrine levels were measured after electrically induced maternal stress and were increased 25%. Maternal stress may decrease uterine blood flow secondary to release of endogenous norepinephrine.