Let’s Talk Contraception: Do Birth Control Pills Cause Blood Clots?

Alarming ads urge you to call a lawyer if you’ve been “injured” taking certain birth control products, such as Yaz, Yasmin, or NuvaRing. These injuries include venous thromboembolisms (VTEs), heart attacks, and strokes. It’s frightening to wonder if you are endangering your health by taking a pill to prevent pregnancy or treat dysmenorrhea (painful cramps).

Should you stop taking your pills? What is a VTE and why should you worry? VTE is a blood clot that usually starts in your leg, but may break loose and travel to your heart or brain and cause a heart attack or stroke. It can be life-threatening, so it is a serious side effect to be concerned about. All birth control pills may increase your risk for a VTE, but it has always been considered so small that most women can safely take the pill. About 3 to 9 women in 10,000 who use birth control pills for more than one year may have a VTE compared to 1 in 5 women out of 10,000 who are not pregnant and not on the pill.


Birth control pills are considered very safe for the majority of women, but all medications carry some risk of adverse effects.


When oral birth control pills were first developed, they contained much higher doses of estrogens and progestins — types of hormones — especially estrogen. It was also noticed that there was a higher risk for developing a blood clot while using birth control pills than in nonpregnant women who didn’t take the pill. It was thought that the high dose of estrogen was responsible for this risk. So, with continuing research and development, eventually the dose of estrogen was decreased to the lower level used today to minimize the chance of a clot. The type of estrogen in pills today is almost exclusively ethinyl estradiol.

Over the years the other hormone in the pill, a progestin, was also studied, and different progestins were developed to lessen uncomfortable side effects linked to that group of hormones, such as bloating, acne, and mood changes. We now have third and fourth generation progesterone hormones that have decreased these side effects greatly. For example, drosperinone is the fourth generation of progestin developed.

However, the risk for blood clots seemed to go up with each new generation of progestin hormone developed. So studies were done, some good and reliable, others with too small a group of participants to be reliable, others with mixed results. Studies are still being done in the United States and in Europe to accurately assess the risk of clots with these new products, including the patch and vaginal ring. As a result of these studies, the Food and Drug Administration (FDA) decided in April 2012 to add a special warning about blood clot risk for contraceptives containing the hormone drosperinone, the hormone in Yaz, Yasmin, and some others. The general thought was that drosperionone increases the risk of a blood clot to 10 women in 10,000 taking contraceptives with drospirenone. That’s double the risk of other pills, but still a small percentage of all women.

Pregnancy also increases your risk of having a VTE — between 5 and 20 women in 10,000 may develop a blood clot during pregnancy. And after delivery, when hormones fluctuate greatly, that risk goes up to somewhere between 40 to 65 women per 10,000.

How do you decipher this information? First, it’s a good idea to know which hormones are in your birth control pill. A good list of contraceptives and their ingredients is available on Medline. Remember, all medications carry some risk of adverse effects. And birth control pills are still considered very safe for the majority of women. The American Congress of Obstetrics and Gynecology is even recommending that they be considered for purchase without a prescription to make contraception more available to women.

How can you decide what your risk is for taking or not taking a birth control pill? A few important suggestions have come from all these studies.

  • It is widely recommended that women over 35 years of age who smoke should probably not use birth control pills. And, no matter your age, you should not smoke while taking any birth control pill. Sometimes your family history or your own health issues might make you a poor candidate for the Pill, and sometimes the risk of pregnancy can be more dangerous to your health than taking the Pill.
  • People with polycystic ovary syndrome (PCOS) might have an even higher risk for blood clots while on the Pill, with blood clots diagnosed in 24 out of every 10,000 pill users with PCOS.
  • Birth control pills are still an excellent choice for many women. It’s important that you discuss your health history and personal needs with your health care provider to decide what is right for you.

There are many contraceptive choices and many birth control pills that contain older formulations of hormones. There are implants, IUDs, and barrier methods. Planned Parenthood is able to help you find the best choice for you. Stop by your local Planned Parenthood health center for more information.


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