Thrombophlebitis causes include disorders related to increased tendency for blood clotting and reduced speed of blood in the veins such as prolonged immobility; prolonged traveling (sitting) may promote a blood clot leading to thrombophlebitis but this occurs relatively less. High estrogen states such as pregnancy, estrogen replacement therapy, or oral contraceptives are associated with an increased risk of thrombophlebitis.[3][4][5] Specific disorders associated with thrombophlebitis include superficial thrombophlebitis which affects veins near the skin surface, deep venous thrombosis which affects deeper veins, and pulmonary embolism.[6] Those with familial clotting disorders such as protein S deficiency, protein C deficiency, or factor V Leiden are also at increased risk of thrombophlebitis. Thrombophlebitis can be found in people with vasculitis including Behçet's disease.