North American Registry of Midwives (NARM) Practice Exam

What is the underlying cause of hemodilution observed during pregnancy?

1. Increased red blood cell production

2. Increased plasma volume

3. Hormonal changes

4. Decreased iron absorption

The correct answer is: Increased plasma volume

Hemodilution during pregnancy primarily occurs due to increased plasma volume. This physiological adaptation is essential in preparing the body for the demands of growing a fetus and supporting the increased blood flow required during pregnancy. As a woman's body prepares for pregnancy, there is a significant increase in blood plasma volume, which can increase by about 30-50% by the third trimester. This expansion contributes to the dilution of red blood cells and other components within the blood, resulting in a lower concentration of red blood cells relative to plasma. This dilution is a normal response that aids in ensuring that adequate blood supply is available for both the mother and the fetus, thus facilitating proper nutrient and waste exchange. While the other options include important aspects of pregnancy, they do not directly explain the phenomenon of hemodilution. Increased red blood cell production occurs as well, but it does not match the rate of plasma volume increase, leaving the net result as hemodilution. Hormonal changes contribute to the overall changes in the circulatory system during pregnancy but are not the direct cause of the hemodilution itself. Decreased iron absorption can affect anemia, yet it is not the primary factor in the relationship between plasma volume and hemodilution during pregnancy. Overall, the