A woman’s physiology goes through an incredible amount of change during pregnancy, affecting virtually every organ system. The number of red blood cells increases as does various clotting factors such as thrombin and fibrinogen. Fibrinolysis decreases, which worsens hypercoagulability. Blood volume actually increases during pregnancy. While iron and folate deficiency may occur, they are not related to increased blood clotting risk. Pregnancy and postpartum periods increase a woman's risk of developing deep vein thrombosis. The increased fluid in circulation because of pregnancy can impact venous blood return, increasing the risk of clot formation. Hormone changes during pregnancy can also increase blood coagulability, increasing the risk of blood clots.