The distribution of blood flow to the reproductive organs of rats near term.

The rate of ovarian and utero-placental blood flow through vessels of less than 25 mum diameter was examined with radioactive microspheres in 5 non-pregnant rats and 19 rats at Day 22 of pregnancy. Total blood flow to the reproductive organs was 0-559 ml/min in the non-pregnant animals and 13-2 ml/min in those near term, a 23-fold difference. The mean ovarian blood flow was high and increased from 0-202 ml/min to 0-845 ml/min. Myometrial and endometrial blood flow increased from 0-156 to 2-24 ml/min. The mean maternal placental blood flow at Day 22 of pregnancy was 0-76 ml/min or 121 ml.,min-1 .100 g-1. Litter size was negatively correlated with mean fetal weight but showed little relationship to mean placental weight or to mean maternal placental blood flow.