I’ve written before that accidental pregnancy is the most serious health risk of many birth control methods. But there are other risks to consider, too. All modern methods of birth control can have positive and negative side effects—Bedsider has information about both for each method. Hopefully anyone who wants to avoid a pregnancy can find an option that has more benefits than drawbacks.
But some types of birth control can be especially risky for women with specific medical conditions. In general, the cautions here apply to hormonal contraceptives that contain both estrogen and progestin—namely, the combination pill, the ring, and the patch. The good news is that while the medical conditions of concern are common in the U.S. as a whole, they aren’t common among young women.
There are a few other conditions that are also of concern, but they’re really rare among women under age 30:
- Heart disease, due to problems with the hearts’ valves or cholesterol build-up in blood vessels
- Liver disease, due to severe cirrhosis or active hepatitis C
- Current breast or liver cancer
Why do these conditions make the pill, patch, and ring riskier?
For each of these conditions, the estrogen hormone in the combination pill, the patch, and the ring may make it worse, or increase the risk of other related medical problems.
- For women with high blood pressure, these methods may make their blood pressure even higher, increasing the risk of a heart attack or stroke.
- For women with migraines with aura, these methods may cause headaches to occur more often, last longer, or be more intense—and this could mean an increased risk of a stroke.
- In the case of a history of stroke, blood clots, or planned bed rest after surgery, these methods may increase the chance of forming a new blood clot.
For young women who are not pregnant and not using a birth control method containing estrogen, the risk of forming a blood clot is low—1 in 5,000 per year. Using a method of birth control with estrogen increases a young woman’s risk of forming a blood clot by several times, and may be as high as 1 in 1,000 per year. (For a sense of scale, pregnancy also increases the risk of forming a blood clot to 1 in 340 per year, and the first month after giving birth is the highest risk time of all—1 in 30.)  For women who have no history of stroke, blood clots, or heart attack, and whose family members have never experienced a blood clot, the risk is still quite low. Women with a history of these medical conditions in their family have a higher risk of forming a new blood clot; adding birth control with estrogen to the mix increases that risk to an unacceptable level.
For women with risk factors for blood clots, not all pills are created equal
There is some evidence that some newer brands of the pill may be more dangerous for women with risk factors for blood clots. This may be due to estrogen in the pill interacting with the other type of hormone in the pill, the progestin. Some newer types of progestin (drospirenone and cyproterone) may cause a higher risk of blood clots compared to older types of progestin (levonorgestrel and norgestrel). Several studies have shown that new progestins about double the risk of a blood clot compared to the older progestins, but other studies have shown no change in risk. We don’t have a definite answer because the studies haven’t been able to account for other risk factors for blood clots, like obesity and smoking.
On the flip-side, progestin-only pills (a.k.a. the mini-pill) are an option for women with these risk factors who want to use the pill. Progestin-only pills don't contain any estrogen.
A note for smokers
Smoking tobacco isn’t a medical condition of its own, but continued smoking does cause all kinds of medical conditions like emphysema, lung cancer, and throat cancer. It can also have an impact on which types of birth control are safe to use. Women under 35 who smoke and have no other medical conditions can usually use the pill with reasonable safety, but should definitely talk to their doctor about alternative methods. Women over 35 who smoke more than 15 cigarettes a day should steer clear of the combination pill, the ring, or the patch.
I have one of these conditions—what should I do?
- Talk to your health care provider about what birth control method is best for you. When you go to your appointment, make sure you complete the form about your and your family’s medical history carefully and accurately. Make a list of your questions beforehand and go over them with your provider.
- Take care of your medical conditions. Some conditions can be treated, making it safer to use methods with estrogen. For example, high blood pressure can usually be treated with diet, exercise, or blood pressure medication.
- Consider genetic testing. Some types of genetic testing can reveal a predisposition for blood clots or stroke (though it’s not clear if a genetic test that shows this predisposition actually predicts that the condition will develop). There are five genetic mutations that are known to increase the risk for blood clots: factor V Leiden, increased prothrombin, decreased antithombin, protein C, or protein S. You can get some types of genetic tests from independent companies, although it’s best to interpret the results with a health care provider.
Now, some good news
Fortunately for women with any of these medical conditions, the increased risk that comes with taking the pill, patch, or ring is totally reversible. A few months after stopping the use of any of these methods, the risk returns to normal. Better still, for women with any of these conditions, there are lots of birth control options that are safe and even more effective than the pill, like the IUD, the implant, or the shot.
 US Centers for Disease Control and Prevention. (2011.) National Health and Nutrition Examination Survey 2009-2010 data.
 Stewart WF, Linet MS, Celentano DD, Van Natta M, Ziegler D. (1991.) Age- and sex-specific incidence rates of migraine with and without visual aura. American Journal of Epidemiology 134(10):1111-20.
 Heinemann LA, Dinger JC. (2007.) Range of published estimates of venous thromboembolism incidence in young women. Contraception 75(5):328-36.
 Reid RL, Westhoff C, Mansour D, et al. Oral contraceptives and venous thromboembolism: Consensus opinion from an international workshop held in Berlin, Germany in December 2009. Journal of Family Planning & Reproductive Health Care 2010; 36(3): 117-122.