What increases risk of pulmonary embolism?

Large proximal DVT: Pulmonary embolus pe could be a clot , air bubble, fat or foreign body . Most commonly a clot, which typically travel from a deep vein thrombosis DVT usually from the legs. The larger the DVT and the more proximal then the more chance of pe . So DVT below the knee rarely causes pe while DVT in thigh veins and iliac veins in the abdomen are at highest risk.

See below: Many things including having had a previous deep venous thrombosis or pulmonary embolism, having a genetic predisposition or family history, smoking, birth control medication, autoimmune diseases such as lupus and prolonged immobilization including travel or bed rest, to name a few.