Distribution of cardiac output in the unstressed pregnant guinea pig.

Cardiac output (CO) and organ flows were measured in five nonpregnant and 14 pregnant unstressed guinea pigs between the thirty-ninth and sixty-fifth postconceptional day by means of radionuclide-labeled microspheres. Blood pressure, heart rate, and cardiac output in nonpregnant animals were 60 torr, 234 bpm, and 248 ml/min, respectively. These parameters did not change significantly during pregnancy. The uterine fraction of cardiac output increased to approximately 18% at term and there was an equivalent decrease in the CO fractions to the carcass and skin. Blood flow per gram of wet weight increased during pregnancy by approximately 140% and 70% for the thyroid and gastrointestinal tract, respectively, but did not change significantly for the heart, brain, kidneys, and adrenals. In pregnant animals near term the weight of the heart, kidneys, intestines, and lungs was approximately 25% lower than that observed in nonpregnant guinea pigs.