Which of the following changes occurs in the mother's cardiovascular system during pregnancy?

The cardiovascular adaptations that occur during pregnancy are crucial for supporting the growing fetus. One significant change is the increase in blood volume, which leads to increased blood flow and demands on the heart. As a result, the mother's blood becomes diluted due to this increased volume, which can lead to a condition known as hemodilution. This means that while the actual components of blood remain the same, the relative concentration can change, which often creates an impression of thicker blood due to the hemodynamic changes.

In contrast, heart rate typically increases during pregnancy as the body works to supply more blood to both the mother and the fetus. Blood pressure may fluctuate throughout pregnancy but usually tends to decrease in the second trimester before rising again later. Peripheral vasculature typically dilates rather than constricts during pregnancy as a response to the increased volume of blood, allowing for better circulation and reduced resistance in the vascular system.

Therefore, the correct choice captures the physiological change in the mother's blood characteristics, as blood does indeed become relatively thicker due to the hemodynamic shifts that accompany pregnancy. Understanding these changes is essential for evaluating the overall health of both the mother and fetus during gestation.