The need to urinate more frequently when pregnant means you’ll have to drink more fluids. Thirst is your body’s normal signal that you and your baby need more fluids. The increased water you drink helps your kidneys rid your body of the extra waste products produced by the baby. You also need more fluids because your blood volume increases to 40 percent when you are pregnant. In addition, your baby needs fluids to fill his or her growing swimming pool (the amniotic sac).