What happens to hematocrit in pregnant women?

In pregnant women, hematocrit decreases primarily due to a phenomenon known as hemodilution. As pregnancy progresses, the body increases its blood volume to support the growing fetus, which includes an expansion in plasma volume. This increase in plasma is proportionally larger than the increase in red blood cell mass, leading to a dilution effect. Consequently, the hematocrit (the ratio of red blood cells to total blood volume) decreases.

This change is a normal and expected physiological adaptation during pregnancy. While there is indeed an increase in red blood cell production to meet the oxygen demands of both the mother and fetus, it does not keep pace with the rise in plasma volume. Thus, hematocrit values tend to fall, aligning with the correct answer and indicating that the body is adapting to support the additional circulatory demands.

Other options suggest that hematocrit might increase, remain stable, or consistently fall below normal levels, which do not accurately reflect the typical changes observed in a healthy pregnancy. The focus remains on the increase in blood volume and its effects on hematocrit levels.