By what percentage does a pregnant woman's blood volume typically increase?

During pregnancy, a woman's blood volume typically increases by 40% to 45%. This significant increase is essential to meet the metabolic demands of both the mother and the developing fetus. Increased blood volume supports the growth of the placenta, provides enough circulating volume to accommodate the increased workload on the heart, and ensures that adequate oxygen and nutrients are delivered to the fetus. This physiological adaptation helps protect against potential complications such as low blood pressure and insufficient oxygen supply, especially during labor and delivery.

The percentage increase in blood volume reflects the body's natural response to the changes in hormonal levels and the increased demands of pregnancy, such as the placental needs and the expansion of maternal tissues. Understanding these changes is crucial for monitoring maternal health throughout the pregnancy.