HEMODYNAMIC-CHANGES DURING PREGNANCY IN THE RABBIT

Blood volume (BV), plasma volume (PV), red cell volume (RCV), cardiac output (CO) and organ blood flows were measured in nonpregnant (Group I), 10-19 days pregnant (Group II) and 20-30 days pregnant (Group III) rabbits. BV, PV and RCV increased throughout pregnancy, with maximum increase during the 2nd third of gestation. CO peaked during the 2nd third of gestation and then decreased. Mean arterial pressure and systemic vascular resistance decreased. Total reproductive blood flow increased throughout pregnancy but when calculated per unit of weight it did not change. Blood flow redistribution within the reproductive organs occurred, with ovarian and placental flow/unit of weight increasing and myometrial flow/unit of weight decreasing. Splenic flow decreased significantly; liver flow decreased. Lung and kidney flow remained unchanged. Major hemodynamic changes evidently occur during the first 2/3 of gestation and this period appears to test the competency of the maternal organism to adapt to the needs of pregnancy. The last 1/3 of gestation is characterized by the fetoplacental unit interaction.