Uterine, maternal placental and ovarian blood flow throughout pregnancy in the guinea pig.

The blood flow to the placenta, uterus, ovaries, and vagina was measured with the aid of radioactive microspheres in thirty pregnant guinea pigs between 22 and 66 days of gestation. The rise in maternal placental blood flow during gestation was ascribable both to an increase in the extent of the vascular bed and to an improvement in relative blood flow from 0.77 ml X min-1 X g-1 at 26--35 days to 1.53 ml X min-1 X g-1 at 56--65 days. The relative rate of blood flow to the subplacenta was constant during the period studied (0.15 ml X min-1 X g-1), although its fraction of total placental blood flow decreased from 10% at 26--35 days to scarcely 1% at 56--65 days. The percentage of total placental weight attributable to the subplacenta during these intervals was 50% and 10% respectively. Perfusion of the uterine tissue decreased during gestation from 0.32 ml X min-1 X g-1 at 26--35 days to 0.18 ml X min-1 X g-1 at 56--65 days. A relation was observed between the weight of and blood flow to an uterine horn and the weight of its contents. Between 22 and 55 days of gestation, ovarian blood flow was related to the number of fetuses in the ipsilateral horn and, in seven unilateral pregnancies, there was a significant difference between the ovarian blood flows on the gravid and non-gravid sides. After day 55 no relation between the ovarian blood flows and the number of fetuses in the ipsilateral horn could be found.