A pregnant client at 28 weeks gestation reports experiencing leg discomfort and noticing bulging veins in her legs. The nurse explains that varicose veins are common during pregnancy. What is the primary physiological change during pregnancy that contributes to the development of varicose veins?

A. Reduced cardiac output: Cardiac output actually increases during pregnancy to meet the demands of the growing fetus. A reduction in cardiac output would not be typical in a healthy pregnancy and is not a contributing factor to varicose veins. B. Dehydration leading to poor circulation: Dehydration may affect overall vascular health but is not a primary cause of varicose veins in pregnancy. Varicosities are more directly related to mechanical and volume changes rather than fluid intake status. C. Decreased progesterone levels: Progesterone levels rise during pregnancy and contribute to venous dilation by relaxing vessel walls. A decrease in progesterone would not support the formation of varicosities and is not physiologically consistent with pregnancy. D. Increased blood volume: Pregnancy causes a 40–50% increase in blood volume, which raises venous pressure, especially in the lower extremities. Combined with uterine pressure on pelvic veins, this leads to vein distension and varicose vein formation.