The first published case report of a blood clot and pulmonary embolism in a woman using Enavid (Enovid 10 mg in the U.S.) at a dose of 20 mg/day did not appear until November 1961, four years after its approval, by which time it had been used by over one million women. It would take almost a decade of epidemiological studies to conclusively establish an increased risk of venous thrombosis in oral contraceptive users and an increased risk of stroke and myocardial infarction in oral contraceptive users who smoke or have high blood pressure or other cardiovascular or cerebrovascular risk factors.
The first documented case of a blood clot and pulmonary embolism associated with Enavid (Enovid 10 mg in the U.S.) at a dose of 20 mg/day appeared in November 1961, four years after its approval. By then, it had been used by over one million women. It took nearly ten years of epidemiological studies to establish an increased risk of venous thrombosis among oral contraceptive users and a heightened risk of stroke and myocardial infarction in those who smoke or have high blood pressure or other cardiovascular or cerebrovascular risk factors.