What change occurs in hematocrit levels during pregnancy?

During pregnancy, hematocrit levels typically decrease. This reduction is primarily due to the expansion of plasma volume, which occurs to accommodate the increased blood flow needed for the developing fetus and to support the mother's physiological changes. Although red blood cell mass does increase during pregnancy, the increase in plasma volume is proportionally greater, leading to a dilutional effect on the hematocrit.

This phenomenon is often referred to as "physiological anemia of pregnancy." It is important to recognize that while the total number of red blood cells increases, the relative proportion of red blood cells to plasma decreases, resulting in a lower hematocrit level. Understanding this adaptation is crucial for healthcare providers, as it helps differentiate normal physiological changes from potential pathological conditions during pregnancy.