Cardiovascular and mammary blood flow alterations during pregnancy and nursing in the rabbit.

The changes in cardiac output, pulse rate, mean arterial pressure, and mammary blood flow were observed during pregnancy and nursing in a chronically instrumented rabbit preparation. Nursing and suckling were found to be associated with significant changes in cardiac output and mammary blood flow. These changes included a progressive increase in cardiac output during pregnancy. In addition, nursing animals had a significantly higher cardiac output than did nonnursing animals. Mammary blood flow was found to increase significantly prior to delivery and reached peak values at 2 weeks after delivery. The relationship between these changes and variables such as litter size, hormonal status, and puerperal stage is discussed in light of the possible physiologic mechanisms which control adaptation during nursing.