Final answer:
Physiologic anemia during pregnancy is due to the dilution of hemoglobin caused by an increased plasma volume, rather than iron intake or erythrocyte production issues. It is a normal adaptation but must be differentiated from iron deficiency anemia, which requires treatment.
Step-by-step explanation:
The rationale for the physiologic anemia that occurs during pregnancy is best described by the dilution of hemoglobin concentration. During pregnancy, the volume of plasma increases, leading to a relative decrease in the concentration of red blood cells (RBCs). This is sometimes referred to as hemodilution. Although the number of RBCs also increases, the plasma volume increases more, resulting in lower hemoglobin concentration and thus physiologic anemia. This adjustment is necessary to meet the increased demand for blood flow and oxygen delivery to both the mother and the developing fetus. It does not necessarily imply inadequate iron intake, decreased production of erythrocytes, or the fetus establishing iron stores as the main reasons for this condition.
It is essential to distinguish this physiological change from iron deficiency anemia, which is also prevalent during pregnancy and can have adverse effects for both the mother and baby. The body needs more iron during pregnancy to produce extra hemoglobin for the additional blood and to provide for the growing fetus and placenta. Iron deficiency can lead to anemia with hemoglobin levels that are lower than the normal pregnancy-adjusted values.