Physiologic anemia of pregnancy is primarily due to:

• A. Decreased plasma volume
• B. Increased red blood cell mass with no change in plasma
• C. Increased plasma volume causing hemodilution
• D. Iron deficiency is present

Answer: (C)

Physiologic anemia of pregnancy happens because plasma volume expands much more than red blood cell mass. The body increases circulating fluid to support the growing fetus, but the production of red cells lags behind this expansion, so the red cells become diluted in a larger volume of plasma. The result is lower hemoglobin and hematocrit values that are normal for pregnancy. This is a normal adaptation and not due to a lack of plasma, nor due to a lack of increase in red cells. Iron deficiency could cause anemia, but that type is not the same dilutional pattern and would typically involve depleted iron stores and different blood indices.