What causes a Deep Vein Thrombosis or Pulmonary Embolism blood clot?
A. There are many known causes of clot formation. Prolonged bed rest or inactivity, such as a long plane ride, can cause reduced circulation in the legs, which provides the opportunity for clot formation. Major surgical procedures or physical trauma can also increase the risk. Blood has several clotting factors, and an imbalance may lead to increased clot formation. There are genetic disorders known to contribute to clot formation. Pregnancy, oral contra-contraceptives, and hormone replacement therapy also increase the risk of clots. Two-thirds of all clots have no identifiable cause, and this is the subject of ongoing research. Two risk factors recently discovered are Factor V Leiden and an elevated homo-cysteine level.
