Yaz, Yasmin may pose higher risk of blood clots

The new, heavily advertised birth control pills Yasmin and Yaz might be more likely to cause potentially deadly blood clots than older oral contraceptives, according to two new studies in the British Medical Journal. While the risk is still uncertain, and the pills might be a good choice for some women, there are other good options to choose from that have longer, better understood safety records.

All birth control pills that combine a progestin with estrogen can cause a deep vein thrombosis (DVT)—a clot in the legs that can cause pain and, if it travels to the lungs, death. In older pills, the risk of having a DVT is quite low, occurring in about one in 10,000 women who take the pills for a year. But the two new studies suggest that the birth control pills Yasmin and Yaz, which combine the progestin drosperinone with estrogen, can cause the clots in about two to three of every 10,000 women.

Some experts question the new findings, pointing out that previous research found no increased blood-clot risk with the newer birth control pills. And they say that the pills, which block menstrual bleeding more completely than older pills, might be an especially good choice for women with problems stemming from hormonal fluctuations, such as endometriosis, irregular or very painful periods, ovarian cysts, abnormal uterine bleeding, and migraine headaches.

On the other hand, the newer pills pose their own side effects, including breast tenderness and breakthrough bleeding, have an uncertain safety record, and tend to cost more.

Bottom line: If you're already taking Yasmin or Yaz you don't need to stop, and shouldn't stop abruptly without talking with a doctor first. That's because pregnancy itself can cause blood clots in about one in 1,000 to 1,500 women. Instead, you should discuss your options with a doctor to see if other contraceptive methods might be appropriate. For example, if you're at high risk of a blood clot because you're obese, smoke, or older than 35 you should generally avoid any birth control pill, patch, or vaginal ring that contains estrogen. Instead, you should usually consider intrauterine devices (IUDs) or progestin-only pills or implants.

Read more about birth control pills, including the newer ones.

Sources
Risk of non-fatal venous thromboembolism in women using oral contraceptives containing drospirenone compared with women using oral contraceptives containing levonorgestrel: case-control study using United States claims data [British Medical Journal]

Risk of venous thromboembolism in users of oral contraceptives containing drospirenone or levonorgestrel: nested case-control study based on UK General Practice Research Database [British Medical Journal]

—Steve Mitchell