What is the most likely cause of anemia in a healthy pregnant woman with normal MCV and MCH values?

In a healthy pregnant woman, the most likely cause of anemia characterized by normal mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) values is the expansion of intravascular volume that occurs during pregnancy.

During pregnancy, women experience a significant increase in blood plasma volume, which leads to what is often described as “dilutional anemia.” This occurs because plasma volume increases more rapidly than red blood cell mass. As a result, while the total volume of red blood cells may not decrease, their concentration in the plasma is diluted, giving rise to lower hemoglobin levels without a reduction in MCV or MCH.

This condition is generally a normal physiological adaptation to support the increased demands of both the mother and the developing fetus, leading to a state where normal or slightly reduced hemoglobin levels are observed without indicating any pathological process.

The other options listed typically involve specific pathological conditions that do not align with the presentation of a healthy pregnant woman experiencing anemia with normal MCV and MCH. Therefore, the expansion of intravascular volume is recognized as the principal factor contributing to this physiological anemia during pregnancy.