Which of the following is a common physical change during pregnancy?

An increase in blood volume is a notable physiological change that commonly occurs during pregnancy. This adaptation is essential to support the growing fetus and provide adequate oxygen and nutrients. By increasing the blood volume, the maternal body can enhance circulation, accommodate the needs of the developing placenta, and prepare for the increased demands of labor and delivery. Typically, blood volume can increase by about 30% to 50% during this time.

In contrast, the other options do not align with the typical changes associated with pregnancy. For instance, skin pigmentation often increases due to hormonal changes, heart rate typically rises to accommodate increased metabolic needs, and hormone levels generally increase to support the pregnancy. Therefore, the correct answer highlights a significant and essential change that supports both maternal and fetal health during pregnancy.