Birth Control and Cardiovascular Risk

Birth Control and Cardiovascular Risk

Medical Disclaimer: This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Information is based on current medical literature and clinical guidelines but may not apply to your specific situation. Individual responses vary based on personal medical history and concurrent conditions. Always consult qualified healthcare providers for medical decisions. Never delay seeking medical care based on content you’ve read. If experiencing a medical emergency, seek immediate medical attention.

These articles provide education to enhance your healthcare partnership. All treatment decisions should involve your healthcare team. Use this knowledge to have informed discussions, not replace medical care.

In Brief

Contraception is a decision about pregnancy prevention, period control, mood, skin, libido, future fertility, and a small number of other things. Cardiovascular risk is one factor among many. For most healthy women without specific risk factors, it is a small factor — small enough that the contraceptive decision should be made on other grounds. For a specific minority of women, it is a large factor, and the right method is decidedly not the estrogen-containing pill, patch, or ring.

The risks of combined hormonal contraception rise sharply in women who smoke after age 35, who have migraine with aura, who have uncontrolled hypertension, who have thrombophilia, who have had a blood clot before, or who have established cardiovascular disease. (1,2,3,4) For women in those categories, effective non-estrogen options exist — the levonorgestrel IUD, the etonogestrel implant, progestin-only pills, the copper IUD. They are not consolation prizes. They are excellent contraceptives that happen not to carry the cardiovascular risk. This article walks through the numbers, names the risk-modifying conditions, and explains what your contraception visit should cover.

How Big the Risks Actually Are

The first thing to understand about combined hormonal contraception and cardiovascular risk is the size of the baseline you are comparing to.

Among healthy young women not using hormonal contraception and not pregnant, the rate of venous thromboembolism — blood clots in the legs or lungs — is approximately 1 to 5 events per 10,000 woman-years. (3) That is a small number. On a low-dose combined oral contraceptive, the rate rises to approximately 3 to 12 per 10,000 woman-years. Pregnancy itself runs at approximately 5 to 20 per 10,000 woman-years. The six weeks after delivery — the highest-risk reproductive state for blood clots — runs at approximately 40 to 65 per 10,000 woman-years. (3)

The pattern matters because the contraceptive conversation is not “use this pill or accept no risk.” It is “use this method or use a different one, and remember that pregnancy itself carries cardiovascular risk.” For a healthy young woman without specific risk factors, the cardiovascular risk of a low-dose combined oral contraceptive is real but small, and substantially lower than the cardiovascular risk of the pregnancy the contraceptive is preventing.

Arterial events — heart attack and ischemic stroke — are less common than clots in this population. The Lidegaard Danish national registry study followed more than 1.6 million women across 14 million woman-years of observation and documented absolute rates of about 21 thrombotic strokes and 10 heart attacks per 100,000 woman-years across the cohort. Combined oral contraceptives with 30 to 40 micrograms of ethinyl estradiol carried relative risks of 1.3 to 2.3 for these events; the 20 microgram formulations 0.9 to 1.7. (1) In absolute terms, doubling a 10-per-100,000 risk produces a 20-per-100,000 risk. Real, but small.

The relative risk framing — “combined oral contraceptives triple your blood clot risk” — is mathematically accurate and rhetorically misleading. Tripling a small number produces a still-small number. The same tripling applied to a woman who is already at high baseline risk produces a much larger absolute increase. Background risk is what determines whether the relative risk matters.

What Drives the Risk

The cardiovascular risk on combined hormonal contraception comes mostly from the estrogen component, not the progestin. Estrogen alters how the liver synthesizes coagulation factors and shifts the blood toward a more clot-prone state. Progestin-only methods, which contain no estrogen, do not produce this shift to the same degree and have a much smaller cardiovascular risk signal. (1,4) That is why the question “which contraceptive is right for me” so often comes down to “do you need estrogen, or will a progestin-only method do.”

Within combined formulations, three secondary factors matter.

Dose. The transition from the 50-microgram ethinyl estradiol formulations of the 1960s and 1970s to the 20- to 35-microgram formulations standard today has substantially reduced absolute event rates. Whether 20-microgram formulations carry meaningfully lower risk than 30- to 35-microgram formulations is less settled — the confidence intervals overlap in the Lidegaard data — but lower-dose generally means lower risk. (1)

Progestin type. The newer-generation progestins — desogestrel, gestodene, drospirenone — have been consistently associated with higher blood clot risk than the older-generation progestins (levonorgestrel, norgestimate). In the Vinogradova analysis of more than 10,000 venous thromboembolism cases, the adjusted odds ratios were approximately 2.4 for levonorgestrel and 2.5 for norgestimate, and approximately 4.1 to 4.3 for desogestrel and drospirenone. (2) In absolute terms, that translated to 6 extra clots per 10,000 woman-years for levonorgestrel and norgestimate versus up to 14 per 10,000 woman-years for the newer progestins. If a combined oral contraceptive is appropriate, levonorgestrel- or norgestimate-containing formulations are the conservative cardiovascular choice. The arterial risk (heart attack, stroke) does not appear to differ as markedly by progestin type.

Your baseline. A 20-year-old non-smoker without other risk factors and a 40-year-old smoker with hypertension can both take the same pill and have the same relative risk increase — but the absolute event rates are wildly different. The relative risks reported in studies are broadly similar across age groups. The absolute risks are not.

Who Should Not Take Combined Hormonal Contraception

This is the part of the article that matters most to the women it most concerns. Combined hormonal contraception is contraindicated — meaning the cardiovascular risk is high enough that major society guidance says do not use it — in the following situations. The 2024 US Medical Eligibility Criteria for Contraceptive Use is the relevant US framework. (4)

Smoker, age 35 or older. Smoking and estrogen each raise cardiovascular risk; the combination is multiplicative rather than additive. Combined hormonal contraception is Category 4 (do not use) for women 35 or older who smoke 15 or more cigarettes daily, and Category 3 (generally not recommended) for women 35 or older who smoke fewer than 15 cigarettes daily. (4) Below 35, the conversation should be about smoking cessation. If you smoke and you are 35 or older, the right combined oral contraceptive is no combined oral contraceptive.

Migraine with aura, at any age. Migraine with aura — the kind preceded by visual symptoms (flashing lights, blind spots, zigzag lines) or other transient neurological symptoms — independently raises ischemic stroke risk. In the Champaloux case-control analysis, the adjusted odds ratio for stroke in women with migraine with aura compared with women without migraine was 2.7. The joint effect with combined hormonal contraception is substantially greater than the sum of the individual effects: women with migraine with aura who used combined hormonal contraception had an adjusted odds ratio of 6.1 (95% CI 3.1–12.1) for ischemic stroke compared with women who had neither. (5)

Champaloux et al., 2017. The joint effect (bottom row) exceeds the sum of the individual effects.

The 2024 US MEC classifies combined hormonal contraception as Category 4 (do not use) in women with migraine with aura at any age. (4,8) Migraine without aura is treated more permissively, with categorization depending on age and other factors. If you have migraine with aura and are currently on a combined oral contraceptive, raise this with your clinician — the alternative methods that are not contraindicated are excellent.

Uncontrolled hypertension. Hypertension and combined hormonal contraception each raise stroke risk; the combination raises it substantially. Combined hormonal contraception is Category 4 if blood pressure is consistently 160/100 mm Hg or higher, and Category 3 to 4 in hypertensive vascular disease. Below those thresholds, the calculation depends on age and other factors. (4)

Known thrombophilia. Inherited disorders that predispose to clotting — Factor V Leiden, prothrombin gene mutation, deficiencies of antithrombin, protein C, or protein S — multiply the clot risk of estrogen-containing contraception substantially. Routine screening before contraceptive prescription is not recommended in the absence of personal or strong family history of clots (the population-level testing burden does not justify the population-level benefit), but if you know you have a thrombophilia, combined hormonal contraception is not the right choice. Antiphospholipid antibody syndrome, an acquired thrombophilia, is Category 4. (4)

Prior venous thromboembolism. A personal history of a blood clot is generally Category 4 for combined hormonal contraception, particularly if the clot was unprovoked or hormone-associated. (4)

Established cardiovascular disease. Coronary artery disease, prior heart attack, prior stroke, complicated valvular heart disease, and other established atherosclerotic vascular disease are Category 4 for combined hormonal contraception. (4)

Multiple cardiovascular risk factors. Older age plus smoking plus diabetes plus hypertension plus dyslipidemia — the cumulative risk profile, rather than any single factor — is also Category 4 even if no individual factor crosses a categorical threshold. (4)

Adverse pregnancy outcomes. A history of preeclampsia, gestational hypertension, gestational diabetes, or preterm delivery — covered in Article 3 of this series — does not categorically contraindicate combined hormonal contraception, but it shifts the background cardiovascular risk profile and belongs in the conversation about method selection.

If you are in any of the Category 4 groups above, the question is not whether you can find a way to keep using a combined oral contraceptive. It is which of the non-estrogen options is right for you. The next section addresses that.

What to Use Instead

The contraceptive options remaining when combined hormonal contraception is contraindicated are not residual. They are excellent.

Levonorgestrel intrauterine devices (Mirena, Liletta, Kyleena, Skyla). Highly effective long-acting reversible contraception, lasting three to eight years depending on the device. Progestin-only and acting primarily locally in the uterus. No cardiovascular risk signal. (4) Often the first-line choice in women with cardiovascular contraindications to estrogen-containing methods.

Etonogestrel subdermal implant (Nexplanon). A small rod placed under the skin of the upper arm, lasting up to three years. Highly effective, progestin-only, no estrogen, no clinically significant cardiovascular risk signal. (4)

Copper intrauterine device (Paragard). The non-hormonal option. No hormones at all. Works through local copper-induced impairment of sperm function. Cardiovascular risk: none. (4) Limitations are unrelated to cardiovascular biology — heavier menstrual bleeding for some women, the small procedural risks of placement.

Progestin-only pills (including newer drospirenone-only pills). Less effective than long-acting methods because they depend on daily adherence, but no estrogen and no clinically significant cardiovascular risk signal in most studies. (4) The principal exception in the progestin-only category is depot medroxyprogesterone acetate, where some studies have suggested a modest blood clot signal, though the magnitude remains debated.

Permanent contraception (tubal occlusion). For women who have completed childbearing, surgical sterilization removes the contraceptive cardiovascular question entirely.

The typical-use failure rates of long-acting reversible methods — the IUDs and the implant — are actually lower than the typical-use failure rate of combined oral contraceptives. (4) The non-estrogen options are not a step down in contraceptive effectiveness. For women with cardiovascular risk factors, they are often a step up.

The Visit Conversation

If you are choosing a contraceptive method for the first time, switching methods, or revisiting a long-running prescription, here is what a good contraceptive visit covers.

Your cardiovascular history, named explicitly. Migraine type (with or without aura). Smoking status and amount. Blood pressure history. Personal or family history of blood clots. Any prior cardiovascular diagnosis. Any history of preeclampsia, gestational hypertension, gestational diabetes, or preterm delivery. These belong in the contraceptive conversation, not just the cardiology conversation.

Whether combined hormonal contraception is the right category at all. If any of the contraindications above apply, the conversation moves to non-estrogen options. If none apply, combined methods are reasonable and the choice among them depends on dose, progestin type, and your preferences.

The right formulation if combined methods are appropriate. Lower-dose ethinyl estradiol (20 to 30 micrograms). Older-generation progestin (levonorgestrel or norgestimate) for the most favorable clot profile, unless there’s a specific reason to choose otherwise. Transdermal or vaginal-ring formulations carry similar cardiovascular profiles to oral combined methods.

A reassessment plan. The right method at 25 may not be the right method at 38. Smoking status changes. Blood pressure changes. Migraine patterns change. The contraceptive method conversation is not a single decision. Revisit it whenever a risk factor changes — and definitely if you start having new aura symptoms on a combined method, which is a reason for immediate reevaluation rather than scheduled follow-up.

The Bottom Line

For the majority of healthy women without specific risk factors, combined hormonal contraception is a safe, effective contraceptive option with a small absolute cardiovascular risk that is meaningfully smaller than the cardiovascular risk of the pregnancy it prevents. The contraceptive decision in this group should be made on other grounds — effectiveness for the indication, side effect profile, convenience, reversibility, and personal preference.

For women with specific cardiovascular risk factors — smoking after age 35, migraine with aura, uncontrolled hypertension, thrombophilia, prior venous thromboembolism, established cardiovascular disease, or multiple cumulative risk factors — combined hormonal contraception is not the right choice. The cardiovascular risk in these subgroups is substantial enough that major society guidance considers them contraindications. The non-estrogen options that remain available — the levonorgestrel IUD, the etonogestrel implant, the copper IUD, progestin-only pills — are highly effective, often more effective in typical use than combined oral contraceptives, and carry no clinically significant cardiovascular risk. No woman in a cardiovascular-risk subgroup should feel that effective contraception requires accepting estrogen-related risk. It does not.

The contraceptive visit should treat cardiovascular risk as one factor in a larger decision, not as the only factor. The right method is the one that prevents pregnancy effectively, fits the life you are living, and does not put you at risk you do not need to take.

Next: Article 5 covers the menopause transition — what happens cardiovascularly as estrogen declines, why midlife is the most under-utilized window for cardiovascular prevention, and what your evaluation should actually include.

Key Terms

Combined hormonal contraceptive (CHC) / Combined oral contraceptive (COC): A contraceptive containing both estrogen and a progestin. Available as oral pills, transdermal patches, and vaginal rings. The cardiovascular risk signal is concentrated in this category.

Ethinyl estradiol: The synthetic estrogen used in most combined hormonal contraceptives. Doses in modern formulations range from 10 to 35 micrograms.

Levonorgestrel: A second-generation progestin used in some combined oral contraceptives, in progestin-only pills, in the levonorgestrel intrauterine device, and in emergency contraception. Carries the most favorable venous thromboembolism profile among progestins commonly used in combined contraception.

Migraine with aura: A migraine subtype characterized by transient neurological symptoms (most commonly visual disturbances) preceding or accompanying the headache. Independently associated with increased ischemic stroke risk and a Category 4 contraindication to combined hormonal contraception.

Progestin-only contraception: Contraceptive methods that contain no estrogen. Includes progestin-only pills, the etonogestrel subdermal implant, depot medroxyprogesterone acetate, and the levonorgestrel-releasing intrauterine devices. Do not carry the cardiovascular risk signal associated with combined contraception.

Thrombophilia: A condition that predisposes to abnormal blood clotting. Includes inherited disorders such as Factor V Leiden, prothrombin gene mutation, and deficiencies of antithrombin, protein C, or protein S, as well as acquired conditions such as antiphospholipid antibody syndrome.

United States Medical Eligibility Criteria (US MEC): A framework published by the Centers for Disease Control and Prevention assigning each contraceptive method a safety category for each medical condition. Most recently updated in 2024.

Venous thromboembolism (VTE): A category of disease that includes deep vein thrombosis (a blood clot in a deep vein, typically of the leg) and pulmonary embolism (a clot that travels to the pulmonary circulation). The most common cardiovascular complication associated with combined hormonal contraception.

References

1. Lidegaard Ø, Løkkegaard E, Jensen A, Skovlund CW, Keiding N. Thrombotic stroke and myocardial infarction with hormonal contraception. N Engl J Med. 2012;366(24):2257–2266.
2. Vinogradova Y, Coupland C, Hippisley-Cox J. Use of combined oral contraceptives and risk of venous thromboembolism: nested case-control studies using the QResearch and CPRD databases. BMJ. 2015;350:h2135.
3. Practice Committee of the American Society for Reproductive Medicine. Combined hormonal contraception and the risk of venous thromboembolism: a guideline. Fertil Steril. 2017;107(1):43–51.
4. Nguyen AT, Curtis KM, Tepper NK, et al. U.S. Medical Eligibility Criteria for Contraceptive Use, 2024. MMWR Recomm Rep. 2024;73(4):1–126.
5. Champaloux SW, Tepper NK, Monsour M, et al. Use of combined hormonal contraceptives among women with migraines and risk of ischemic stroke. Am J Obstet Gynecol. 2017;216(5):489.e1–489.e7.
6. World Health Organization. Medical Eligibility Criteria for Contraceptive Use. 5th ed. Geneva: World Health Organization; 2015.
7. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 206: Use of Hormonal Contraception in Women With Coexisting Medical Conditions. Obstet Gynecol. 2019;133(2):e128–e150.
8. Sacco S, Merki-Feld GS, Ægidius KL, et al; European Headache Federation (EHF); European Society of Contraception and Reproductive Health (ESC). Hormonal contraceptives and risk of ischemic stroke in women with migraine: a consensus statement from the European Headache Federation (EHF) and the European Society of Contraception and Reproductive Health (ESC). J Headache Pain. 2017;18(1):108.