Uterine and ovarian artery blood flow in the pregnant dog. Attempt at comparative study in pregnant women.

UABF and OABF were measured in dogs with the electromagnetic flowmeter. In eight nonpregnant animals, UABF was on the average 3.2 ml/min and OABF 0.4 ml/min. In 10 pregnant bitches near term UABF was 27.3 ml/min and OABF 1.3 ml/min. Complete aortic occlusion in the pregnant bitch at term reduces UABF to 2.4 ml/min (loss of 24.9 ml/min) and increases OABF to only 1.6 ml/min (gain of 0.3 ml/min). The conclusion is that most of the blood flow to the uteroplacental unit in the pregnant bitch is channelled through the uterine artery and the marked drop in UABF produced by acute aortic occlusion is not compensated by an increase in OABF. The conditions are different in human pregnancy where the progressive nature of the aortic compression by the pregnant uterus allows, under the most favorable circumstances, the gradual development of a collateral circulation mostly through the ovarian arteries. However, this does not occur all the time as demonstrated by angiographic studies in a series of 12 patients and in similar studies reported in the literature. This could result in a placental insufficiency.