Identify a key hematological change that characterizes pregnancy physiology.

During pregnancy, one of the most significant physiological changes is the expansion of plasma volume. This increase can be attributed to various factors, including hormonal changes and the body's adaptation to support both the mother and growing fetus. A substantial increase in plasma volume helps to accommodate the extra blood flow required during pregnancy, which is vital for optimal oxygen and nutrient delivery to the placenta and fetus.

This increased plasma volume also results in a dilutional anemia, as the rise in plasma volume does not lead to a proportional increase in red blood cell production, leading to lower hemoglobin concentration. The body adjusts to these changes to ensure effective blood circulation and metabolic demands are met during this critical period. Understanding this key hematological change is essential for recognizing how pregnancy alters normal physiological processes and for monitoring maternal-fetal health.