Which of the following is NOT a risk factor for pulmonary embolism?

Risk factors for pulmonary embolism are thrombophilias like factor V leiden mutation, protein C, S deficiency, APLA syndrome. Other common predisposing factors include cancer, systemic aerial hypeension, chronic obstructive pulmonary disease, long-haul air travel, air pollution, obesity, cigarette smoking, eating large amounts of red meat, oral contraceptives, pregnancy, postmenopausal hormone replacement, surgery, and trauma. Progesterone therapy is not specifically mentioned as a cause of pulmonary embolism. Ref: Harrisons principles of internal medicine, 18th edition, Page: 2170.