What characterizes the physiological anemia of pregnancy?

The physiological anemia of pregnancy is characterized primarily by an increase in plasma volume. During pregnancy, the body undergoes significant changes to support the growing fetus, and one of those changes is an increase in total blood volume. This expanded plasma volume creates a dilutional effect on red blood cells, which can lead to a lower concentration of hemoglobin and hematocrit levels, giving the appearance of anemia despite the actual red blood cell mass typically being adequate.

This physiological adaptation is necessary to ensure that there is sufficient blood flow and oxygen delivery to both the mother and the fetus. The increase in plasma volume is part of the body's strategy to meet the heightened metabolic demands during pregnancy, including providing nutrients and supporting increased uterine and placental weight.

The other choices do not accurately describe the main characteristic of physiological anemia in pregnant individuals. A decrease in red blood cell production usually indicates a pathological condition rather than a physiological state, and inadequate dietary iron is not a defining characteristic of physiological anemia, although it may lead to iron deficiency anemia. Increased blood viscosity is less relevant in this context, as the dilution effect from the plasma increase generally lowers viscosity rather than increasing it.