What is the expected percentage increase in blood volume during pregnancy?

During pregnancy, a significant physiological change occurs in a woman's body to support the developing fetus, primarily involving an increase in blood volume. This increase is essential for accommodating the needs of the growing placenta and fetus, ensuring adequate oxygen and nutrient delivery while also preparing for the blood loss that might occur during childbirth.

The expected percentage increase in blood volume during pregnancy is approximately 40-50%, with many sources commonly citing around 45% as a typical figure. This substantial increase is due to several factors, including increased plasma volume (which rises significantly more than red blood cell mass) and the body's efforts to maintain hemodynamic stability despite the increased demands placed on it.

The percentage increase supports enhanced cardiac output and helps to prevent potential complications such as hypotension. Additionally, the increase in blood volume helps in the expansion of circulating blood volume to meet the metabolic needs of the mother and fetus.

While some sources may vary slightly, the correct answer of 45% accurately reflects the average increase observed in clinical practice, making it the most realistic estimation of blood volume expansion during pregnancy.