Why do your feet swell when you're pregnant?

Because you're retaining more water. Changes in your blood chemistry also cause some fluid to shift into your tissue. In addition, your growing uterus puts pressure on your pelvic veins and your vena cava (the large vein on the right side of the body that carries blood from your lower limbs back to the heart). The pressure slows the return of blood from your legs, causing it to pool, which forces fluid from your veins into the tissues of your feet and ankles. And sometimes even in your hands.