Extreme changes during pregnancy were compared with the mean postpartum values of the same animals. Those characteristics which changed significantly during pregnancy were: body weight increased 15%, peaking at term (30.1 Vs 26.1 kg; p < 0.01); heart rate was elevated 32% at term (115 vs 87 beats/min; p < 0.01); arterial systolic pressure dropped 7% (115 vs 124 mmHg; p < 0.05); arterial diastolic pressure dropped 9% (81 vs 89 mmHg; p < 0.05) and mean arterial pressure dropped 8% (99 vs 107 mmHg; p < 0.05), all being lowest at 16-18 wks of pregnancy; plasma volume was elevated 13% (1.56 vs 1.38 liters; p < 0.05) and blood volume 11% (2.16 vs 1.95 liters; p < 0.05) both peaking at term; cardiac output increased 48% (5.32 vs 3.60 liters/min; p < 0.01) and cardiac output/kg increased 29% (182 vs 141 ml/kg/min; p < 0.05) both peaking at term; stroke volume was elevated 10% at term (46.5 vs 42.3 ml/stroke; p < 0.05); peripheral vascular resistance decreased 37% being lowest at term (1531 Vs 2440 dyne-sec-cm^-5; p < 0.01); hemoglobin flow was elevated 42% at term (501 vs 353 g/min; p < 0.05) and hemoglobin flow/kg body wt was elevated 31% at 16-18 wks of gestation (18.3 vs 14.0 g/kg/min; p < 0.05).

Those characteristics which showed no significant (p > 0.05) change during pregnancy were: mean pulmonary artery pressure, systemic arterial pulse pressure, hematocrit, hemoglobin concentration, red cell volume and blood volume per kilogram.