Combined hormonal contraception (CHC) methods are birth control methods containing the hormones estrogen and progestin. Tens of millions of people safely use CHCs—including birth control pills, patches, and vaginal rings—to help space births and prevent unintended pregnancy.
All CHCs carry a small, increased risk of blood clots, though this risk is significantly smaller than the risk of blood clot associated with pregnancy. Venous blood clots—also known as venous thromboembolisms (VTEs)—are a mass of thickened blood inside a person’s vein. They can travel through the bloodstream, potentially resulting in damage to vital organs or death.
While all CHCs carry some risk of blood clots, that risk can differ based on the method. The fact sheet below provides background information on the relative risk of different CHCs as well as warning signs everyone should be aware of. But those concerned about the increased risk of blood clots should speak with their health care provider or pharmacist about their risk as well as their contraceptive options.
Why does combined hormonal contraception increase blood clot risk?
Increased estrogen levels are associated with increased blood clot risk. Taking CHCs increases the body’s estrogen levels and estrogen increases the blood’s ability to clot. Therefore, CHCs increase the risk of developing a blood clot.
In addition to estrogen, some studies suggest that the progestin hormones drospirenone and desogestrel may also increase the blood’s ability to clot. These progestins are used in some CHCs such as Yaz®, Yasmin®, and Desogen®. In 2011, the NWHN argued against continued FDA approval of drospirenone pills arguing that they may heighten the risk of blood clots without providing a unique benefit over other available options. (Click here to read more about our position.)
The science behind the risk of blood clots with these progestins is still emerging, and people concerned about the possible increased risk should speak with their health care provider.
Do some combined hormonal contraceptive methods have a higher blood clot risk than others?
Research indicates that both the patch and vaginal ring have a higher risk of blood clots than most pills. One study found that people using the vaginal ring were 1.9 times more likely to experience a blood clot than people taking combination birth control pills. In this same study, people using the patch were 2.3 times more likely to experience a blood clot than people taking combination birth control pills.1
How often do blood clots occur?
Blood clots are generally rare but sometimes occur in otherwise healthy people, even those not taking CHCs. Between 1 and 5 of every 10,000 women (who are not pregnant and not using CHCs) will experience a blood clot in any given year.2 This number increases slightly if the person uses CHCs. Between 3 and 9 of every 10,000 CHC users will experience a blood clot in any given year.3
However, the highest risk of blood clots for reproductive-aged women occurs during pregnancy and after giving birth (the postpartum period). This is because women’s estrogen levels increase during this time. Between 5 and 20 of every 10,000 pregnant women, and 40 to 65 of every 10,000 postpartum women, will experience a blood clot in any given year.4 So even though CHCs increase the risk of blood clots for its users, this risk is only slightly higher than for non-users and significantly less than the risk associated with pregnancy.
What are the signs and symptoms of blood clots?
Depending on where in the body the blood clot is located, people may experience some or all of the following symptoms:
- redness of the skin
- difficulty breathing
- faster than normal or irregular heartbeat
- chest pain or discomfort
- coughing up blood
- very low blood pressure, lightheadedness, or fainting5
People experiencing any of the above symptoms should seek medical care immediately. Some people experiencing a blood clot, however, have no signs or symptoms at all.
Are there other factors that increase blood clot risk?
People who do not use CHCs may have personal characteristics or medical conditions which increase their risk of blood clots. These include, but are not limited to:
- overweight or obesity
- genetic clotting disorders
- advanced age (60+)
- prolonged inactivity (such as long car or airplane rides)
Individuals with characteristics that place them at higher risk of experiencing blood clots are encouraged to discuss the risks of using CHCs with their health care provider or pharmacist.
What contraceptive options are available for people with an increased risk of blood clots?
People with an increased risk of blood clots have other contraceptive options from which to choose. In fact, the most effective contraception does not contain estrogen and is not associated with a higher risk of blood clots, although each has its own unique benefits and risks to consider. These methods include the arm implant (Nexplanon®) and intrauterine devices (IUDs), such as ParaGard®, Mirena®, Skyla®, and Liletta®. The Depo Provera® shot, progestin-only pills, condoms, and diaphragms are also estrogen-free and safe to use for those with a high risk of blood clots. It should be noted that emergency contraception (Plan B®, or the “morning after” pill) does not contain estrogen and therefore does not increase one’s risk of blood clot.
Are there benefits to combined hormonal contraception besides pregnancy prevention?
CHCs offer many benefits. In addition to preventing unintended pregnancy, CHCs may protect against ovarian and endometrial cancer, heart disease, and ectopic pregnancy (a pregnancy outside of the uterus). CHCs can also reduce pain during menstruation, heavy menstrual bleeding, facial hair growth, acne, and symptoms associated with premenstrual syndrome (PMS), and polycystic ovarian syndrome (PCOS).
Should combined hormonal contraception be taken off the market?
CHCs carry very little risk for most people—in fact, they are one of the most studied and safest medications available today. The pill, patch, and vaginal ring each meet a unique need, so it’s important that a broad range of methods are available. While both the patch and vaginal ring expose users to higher doses of hormones than pills, eliminating the need to take a daily pill may be worth the small increased risk for some.
How do I know which method is best for me?
Contraceptive users need complete information about the risks and benefits of each contraceptive method to determine which method, or combination of methods, is best for them. Individuals are encouraged to discuss the risks and benefits of different contraception options with a qualified health care provider or pharmacist.
For more information on blood clots and contraception, please visit:
- Combined hormonal oral contraception and risk of venous thromboembolism (VTE), The World Health Organization
- Deep Vein Thrombosis (DVT)/Pulmonary (PE) – Blood Clot Forming in a Vein, The Center for Disease Control and Prevention
- Risk of Venous Thromboembolism Among Users of Drospirenone-Containing Oral Contraceptive Pills, The American Congress of Obstetricians and Gynecologists
1. Specifically, this study compared the patch and vaginal ring to levonorgestrel containing combined oral contraception pills. Lidegaard, Øjvind, Lars Hougaard Nielsen, Charlotte Wessel Skovlund, and Ellen Løkkegaard. Venous thrombosis in users of non-oral hormonal contraception: follow-up study, Denmark 2001-10. BMJ 344:e2990 (2012).
2. FDA Drug Safety Communication: Updated information about the risk of blood clots in women taking birth control pills containing drospirenone, U.S. Food & Drug Administration, accessed July 1, 2013, http://www.fda.gov/Drugs/DrugSafety/ucm299305.htm.
5. Centers for Disease Control and Prevention. “Venous Thromboembolism (Blood Clots).” Last modified August 17, 2015. Accessed November 20, 2015. http://www.cdc.gov/ncbddd/dvt/facts.html.
This factsheet is meant to provide current and potential contraceptive users with information to help weigh the risks and benefits of using hormonal contraception. Readers are encouraged to consult their health care providers and/or pharmacists for a more detailed discussion of the risks of using combined hormonal contraception.