The Buzz Around the Pill: Birth Control and the Risk of Blood Clots

Dr. Sharon Orrange
Dr. Orrange is an Associate Professor of Clinical Medicine in the Division of Geriatric, Hospitalist and General Internal Medicine at the Keck School of Medicine of USC.
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Many folks have heard the news, and seen ads on the side of buses: if you took oral contraceptives and have had a deep vein thrombosis (DVT), call some attorney’s number. The reason that a DVT is scary, as you know, is that it can break off and travel up to the lung where it is called a pulmonary embolism. Pulmonary emboli (PE) are dangerous, though when caught early they can be treated with blood thinners.
CC by Sarah C
Well, this is not new and yes, estrogen increases your risk of a clot in the leg, but it is incredibly rare. Vanity Fair ran an article in January 2014 about Nuvaring and death from PE and many patients came in afraid of their pills. Here are the facts, not fiction:

  1.  Risk without birth control. A common estimate of risk for DVT and PE in women ages 15 to 44 years who are not pregnant and not using combined hormonal contraception is 5 to 10 cases per 100,000 woman-years. This means 5 to 10 of 100,000 women followed for a full year may get a clot even while NOT on birth control.

  2.  The risk of clot increases when you take estrogen medications. For combined oral contraceptives, the increase in risk is two- to four-fold, depending upon whether the progestin is second generation (levonorgestrel as in Jolessa and Seasonale), third generation (desogestrel as in Ortho-Cept, DesogenApri) or fourth generation (drospirenone which is in Yasmin or Yaz).

  3.  In general, the lowest clot risk is seen with estrogen-progestin contraceptives that use the progestin levonorgestrel. As listed above this includes pills like Alesse, Aviane, Lutera, Levora, Jolessa, and Seasonale among others.

  4.  Know that the actual increase in risk of clot while taking birth control pills (the absolute risk) among users is 20 to 30 per 100,000 woman-years. This is 20 per 100,000 for second generation oral contraceptives and 30 per 100,000 for contraceptives containing desogestrel or drospirenone. So the risk is 30 per 100,000 users taking a pill for a year if you are using Yasmin, Yaz, Apri, Mircette, Reclipsen, or one of the others.

  5.  Compare this to the absolute risks of clot during pregnancy, which is 60 to 96 per 100,000 woman-years, or being postpartum, where it is 511 per 100,000 woman-years.

  6.  The point here is that combined hormonal contraception is clearly a safe alternative to unwanted pregnancy, and many of you take them to regulate painful periods and treat acne, among other things.

  7.  There is also some good science that shows we are underestimating the risk of clot in those NOT taking birth control which makes your absolute risk when you add oral contraceptives even lower.

  8.  In summary, there have been concerns that newer progestins (listed above) are associated with a greater risk of clot compared to other types of progestins. The absolute excess risk is extremely small, and the many benefits of combined hormonal contraceptives outweigh those risks. Of course you can ask to switch to one that carries a slightly lower risk.

  9.  If you are someone who has a FIRST-DEGREE relative (mom/dad/brother/sister) who had a DVT or PE that was not provoked (meaning it did not happen after a long car drive or flight, or after surgery) you should be tested for inherited forms of clotting disorders. Your doctor can test you for Factor V Leiden and if you do have that, you will not take hormonal contraceptives.

  10.  If you are someone on a birth control pill and you have swelling of one leg and not the other (calf especially) see us right away.

Dr O.

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