Why does the mother’s cardiac output increase during pregnancy?

During pregnancy, a woman’s cardiac output—the volume of blood the heart expels per minute—increases to meet the growing metabolic demands of both the fetus and the mother’s own tissues.1

This physiological adjustment is necessary because the developing fetus and the expanding maternal structures require a continuous supply of oxygen and nutrients, which are delivered via the circulatory system. As the pregnancy progresses, the heart must work harder to circulate this larger volume of blood, leading to an increase in cardiac output that typically peaks between the 28th and 30th weeks of gestation.12

This increased workload is supported by several cardiovascular changes, including a rise in the amount of blood expelled per beat and a more rapid pulse rate. While the heart’s workload is significant, a healthy heart generally manages these demands without undergoing substantial enlargement.1