There are concerns that Bayers Yaz and Yasmin may raise women's risk of blood clots more than other pills.
Two studies published in April in the British Medical Journal found women taking these newer pills were two to three times more likely to develop blood clots in the veins of the legs than women using older pills. But other studies have not reported that increase.
For now, the FDA is not recommending women stop taking birth control pills. The risk is low. But women are advised to watch for symptoms including persistent leg pain, severe chest pain or sudden shortness of breath.