The effect on fetal development and utero-placental blood flow of ligating a uterine artery in the rat near term.

The uterine artery of one horn of 13 rats was ligated on day 18 of gestation; the remaining horn was used as a control. The effect, four days later, on blood flow to the reproductive tract, was measured with radioactive microspheres and compared to the effect on fetal and placental weights. Fetal survival in the ligated horns, 41 percent, was significantly lower (P less than 0.05) than that in the control horns, 98 percent. Fetal and placental weights of the survivors in the ligated horns, 3.159 +/- 0.133 g (SE) and 450 +/- 18 mg respectively, were similarly lower than those in the control horns, 3.814 +/- 0.111 g and 529 +/- 27 mg respectively. Maternal placental blood flow closely reflected the weight of tissue being supplied and was similar in the ligated and control horns, 129 +/- 21 and 130 +/- 18 ml.min(-1). 100g(-1), respectively. Myometrial blood flow was again similar in the ligated and control horns, 34 +/- 5 and 37 +/- 4 ml.min(-1). 100 g(-1), respectively, and in the ovarian, middle and cervical sections of each horn. These results are compatible with the view that ligation causes only a temporary reduction in uterine blood flow which permanently checks placental and fetal, or placental thus fetal, growth. Blood flow then returns to normal levels compatible with the reduced weights of tissues being supplied.