Hormonal Birth Control & Blood Clot Risks
Access to safe, effective contraception is essential to women’s lives. The NHWN believes that women must have complete information about the risks and benefits of various birth control methods so they can make an informed decision about what is best for them and their lives. Many women may be surprised to learn that some types of birth control contain a combination of hormones that increases the risk of blood clots, which have the potential to cause harm. This article provides information on the relative risk of blood clots, and the warning signs about which women should be aware.
What are CHCs?
Birth control that contains the hormones estrogen and progestin together are called Combined Hormonal Contraception (CHCs); CHC contraceptive methods include birth control pills, patches, and vaginal rings. While all CHCs carry some risk of blood clots, the risk can differ based on the specific birth control method a woman uses.
How common are blood clots?
A mass of thickened blood inside a vein is called “venous blood clots” or venous thromboembolisms” (VTEs). Many people are familiar with deep vein thrombosis (DVT) and pulmonary embolism (PE), which are types of VTE. VTEs can travel through the bloodstream, damaging vital organs and even resulting in death. VTEs are the third-most common type of cardiovascular illness in the U.S., and cause 300,000 deaths annually.
Blood clots are generally rare, but sometimes happen to otherwise healthy people, even those who are not taking CHCs. Between 1 and 5 in every 10,000 women who are neither pregnant nor using CHCs experience a blood clot annually. Women using CHCs have a slightly higher risk: between 3 and 9 in every 10,000 CHC users experience a blood clot in a given year.2
It is important to keep in mind that the highest risk of blood clots among reproductive-aged women occurs during pregnancy and in the postpartum period, when estrogen levels increase. Among pregnant women, between 5 and 20 in every 10,000 pregnant women will experience a blood clot in a year; 40 to 65 in every 10,000 postpartum women experience a blood clot in a year.2
So, although CHCs increase the risk of blood clots, the risk is only slightly higher than the risk for women who don’t use CHCs, and is significantly lower than pregnant women’s risk.
Why does CHC increase the risk of blood clots?
Estrogen increases bloods’ ability to clot. So, taking estrogen-containing CHCs increases the body’s estrogen levels, and therefore increases the risk of a blood clot.
Some studies also suggest that the progestin hormones drospirenone and desogestrel may also increase the blood’s ability to clot. These newer-generation progestins are used in CHCs including Yaz®, Yasmin®, and Desogen®. In 2011, the NWHN recommended that the Food and Drug Administration (FDA) reverse its approval of drospirenone pills, due to the method’s heightened risk of blood clots and lack of unique benefits over other contraceptive options. There are specific concerns about the health risks of Yasmin®, which is manufactured by Bayer. The FDA has reprimanded Bayer for its misleading ads that overstated the pills’ benefits and downplayed risks, and for delaying reports about blood clots to the FDA during the approval process.3
In 2012, the FDA reviewed studies on drospirenone-containing birth control and found the method may be associated with an increased risk of clots compared to other progestin-containing contraception. The FDA did not conclude there was a causal relationship, however. The science behind the risk of blood clots with these progestins is still emerging.
Do some combined hormonal contraceptive methods have a higher blood clot risk than others?
Research indicates that the patch and vaginal ring have a higher risk of blood clots than most oral contraceptive pills. One study found that women using the vaginal ring were 1.9 times more likely to experience a blood clot than those taking combination birth control pills. In this study, women using the patch were 2.3 times more likely to experience a blood clot than those taking combination birth control pills. (The research compared the patch and vaginal ring to levonorgestrel-containing combined oral contraception.)
What are the signs and symptoms of blood clots?
Some people experiencing a blood clot have no signs or symptoms at all. When symptoms do occur, depending on where the blood clot is located in the body, people may experience some or all of the following:
• 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 fainting
People experiencing any of these symptoms should seek medical care immediately.
What factors increase the risk of blood clot?
Some personal characteristics and medical conditions increase the risk of blood clots, including (but not limited to):
• overweight or obesity
• genetic clotting disorders
• being over age 60
• prolonged inactivity (such as during long car or airplane rides)
Individuals with characteristics that increase their risk of blood clots should discuss the risks of using CHCs with their health care provider and/or pharmacist.
What contraceptive options are available for women with increased risk of blood clots?
There are other contraceptive options that are preferable for women who are at increased risk of clots. In fact, the most effective contraception methods do not contain estrogen and are not associated with a higher blood clot risk. These include the arm implant (i.e., Nexplanon®) and intrauterine devices (IUDs), such as ParaGard®, Kyleena®, Mirena®, Skyla®, and Liletta®. Each of these methods has its own unique benefits and risks that potential users should consider.
In addition, Depo Provera®, progestin-only pills, condoms, and diaphragms are all also estrogen-free, and safe for women with a high blood clot risk. Emergency Contraception (i.e., Plan B®, One-Step®, and Take Action®) does not contain estrogen, so it does not increase blood clot risks.
Do CHCs offer benefits in addition to pregnancy prevention?
Yes. In addition to preventing unintended pregnancy, CHCs may reduce the risk of developing ovarian and endometrial cancer, heart disease, and ectopic pregnancy (a pregnancy occurring outside the uterus). CHCs can also reduce menstrual pain and heavy 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, CHCs are one of the most-studied and safest medications available today. The pill, patch, and vaginal ring each meets a unique need, and their availability is important in order to ensure that women can access a broad range of methods that suit their specific circumstances.
While the patch and vaginal ring both expose users to higher doses of hormones than pills, women may find the benefits of not having to take a pill every day to be worth the small increased risk. (As noted, the NWHN believes that drospirenone should be taken off the market, for the reasons presented above.)
How do I know which method is best for me?
All contraceptive users need complete information about the risks and benefits of each potential method, so they can determine what method (or combination of methods) is best for them. Women who are concerned about the increased risk of blood clots and other potential risks and benefits of various contraceptive options should talk with a qualified health care provider and/or pharmacist.
• The World Health Organization: Combined Hormonal Oral Contraception and Risk of Venous Thromboembolism (VTE)
• The Centers for Disease Control and Prevention: Deep Vein Thrombosis (DVT)/Pulmonary (PE) – Blood Clot Forming in a Vein
• The American College of Obstetricians and Gynecologists, Committee on Gynecologic Practice: Risk of Venous Thromboembolism Among Users of Drospirenone-Containing Oral Contraceptive Pills.
Ozaki A, Bartholomew JR, Venous Thromboembolism (Deep Venous Thrombosis & Pulmonary Embolism), Cleveland: Cleveland Clinic Center for Continuing Education, 2012. Online:
U.S. Food & Drug Administration (FDA), FDA Drug Safety Communication: Updated information about the risk of blood clots in women taking birth control pills containing drospirenone, Rockville (MD): FDA, 2013. Online: http://www.fda.gov/Drugs/DrugSafety/ucm299305.htm.
Allina A, “Contraceptive Safety Concerns: What’s a Responsible Feminist to do?” The Women’s Health Activist 2012; 37(3):4-5 . Online: https://www.nwhn.org/contraceptive-safety-concerns-whats-a-responsible-feminist-to-do/#sthash.d228fFku.dpuf.
American College of Obstetricians and Gynecologists, Committee on Gynecologic Practice, “Risk of venous thromboembolism among users of drospirenone-containing oral contraceptive pills (Committee Opinion No. 540),” Obstet Gynecol 2012;120:1239–42. Online: https://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Gynecologic-Practice/Risk-of-Venous-Thromboembolism.
Lidegaard Ø, Hougaard Nielsen L, Skovlund CW, and E Løkkegaard. “Venous thrombosis in users of non-oral hormonal contraception: follow-up study, Denmark 2001-10,” BMJ 2012; 344:e2990.
Centers for Disease Control and Prevention (CDC), Venous Thromboembolism (Blood Clots),” Atlanta: CDC, 2015. Online: http://www.cdc.gov/ncbddd/dvt/facts.html.
Batur P, Female Contraception, Cleveland: Cleveland Clinic Center for Continuing Education, 2016. Online: http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/womens-health/female-contraception/