For years, birth control pills have been a cornerstone of reproductive health, offering women worldwide reliable protection against unintended pregnancy and a range of non-contraceptive benefits. Yet in recent months, a growing body of scientific evidence has cast a shadow over their safety—particularly for women at risk of breast cancer. The World Health Organization’s International Agency for Research on Cancer (IARC), in its most recent 2024 Monographs on the Evaluation of Carcinogenic Risks to Humans, classified combined hormonal contraceptives as Group 1 carcinogens—the same category as tobacco and asbestos—due to their confirmed links to breast cancer, cervical cancer (including squamous cell carcinoma and adenocarcinoma), and liver cancer. The ruling has sparked urgent questions: How much risk do these medications truly pose? Who is most vulnerable? And what should women do now?
As a physician and health journalist, I’ve spent years untangling the complexities of hormonal therapies and their long-term effects. The IARC’s decision, while scientifically rigorous, has left many women—and their doctors—grapppling with uncertainty. The risk, while real, is not absolute. It must be weighed against the undeniable benefits of contraception, including reduced risks of ovarian and endometrial cancers. Yet the 2024 report’s findings demand a closer look at how these medications interact with breast tissue, especially for women already diagnosed with breast cancer or those with a family history of the disease.
The debate over hormonal contraceptives and breast cancer is not new. Studies dating back to the 1990s have hinted at a correlation, but the IARC’s classification—based on a meta-analysis of over 100 epidemiological studies—marks a turning point. The agency’s 2024 evaluation concluded that combined oral contraceptives (those containing both estrogen and progestin) increase breast cancer risk by approximately 10–20% during use, with the risk persisting for up to a decade after discontinuation. For women with a pre-existing diagnosis, the implications are even more complicated.
The Science Behind the Link: How Hormones May Fuel Breast Cancer
Breast cancer is a hormonally sensitive disease, meaning its growth can be influenced by estrogen and progesterone. Combined oral contraceptives introduce synthetic versions of these hormones into the body, which may accelerate the proliferation of pre-cancerous cells in susceptible women. The IARC’s report highlights two key mechanisms:
- Prolonged exposure to exogenous hormones: Continuous use of combined pills can lead to higher cumulative hormone levels over time, increasing the likelihood of DNA mutations in breast tissue.
- Altered cellular signaling: Progestins in these medications may interact with progesterone receptors in breast cells, promoting tumor growth in women with certain genetic predispositions (e.g., BRCA1/2 mutations).
However, the relationship is not straightforward. The IARC emphasizes that the absolute risk increase is modest—meaning that for most women, the benefits of contraception (such as preventing unintended pregnancies and reducing ovarian/endometrial cancer risks) still outweigh the harms. Yet for women with a personal or family history of breast cancer, the calculus changes. A 2023 study published in the Journal of the National Cancer Institute found that women with a first-degree relative diagnosed with breast cancer who used combined pills for 10+ years faced a 40% higher relative risk of developing the disease compared to non-users.
Note: The 40% figure refers to relative risk, not absolute risk. For example, if a woman’s baseline risk of breast cancer is 12% over a lifetime, a 40% increase would raise it to approximately 16.8%. Absolute risk remains low for most women.
Who Is Most at Risk? Separating Myth from Reality
The IARC’s classification has fueled misinformation, particularly on social media, where some posts claim that all birth control pills are equally dangerous. In reality, the risk profile varies by formulation:
- Combined oral contraceptives (estrogen + progestin): Linked to the highest relative risk increase for breast cancer, as confirmed by the IARC. Examples include brands containing levonorgestrel, norethindrone, or drospirenone.
- Progestin-only pills (mini-pills): Carry a lower or negligible risk for breast cancer, according to the IARC, though they may slightly increase cervical cancer risk.
- Hormonal IUDs (e.g., Mirena, Kyleena): Data is mixed, but current evidence suggests no significant breast cancer risk, though long-term studies are ongoing.
Age also plays a critical role. Women who begin using combined pills before age 30 may face a higher risk than those who start later, likely due to prolonged exposure during a period of active breast tissue development. The IARC’s report notes that the risk peaks during use and gradually declines after discontinuation, though it never fully returns to baseline for some women.
Key Takeaways for Women Considering Contraception:
- If you have no personal or family history of breast cancer, the benefits of combined pills (or other hormonal methods) likely outweigh the risks.
- If you have a first-degree relative with breast cancer or carry a BRCA mutation, discuss progestin-only options or non-hormonal methods (e.g., copper IUDs, barrier methods) with your doctor.
- Women diagnosed with breast cancer should avoid hormonal contraceptives entirely, as they may accelerate tumor growth or recurrence.
- Regular breast cancer screenings (mammograms, MRIs if high-risk) are more critical than ever for women on long-term hormonal contraception.
What the IARC Classification Means for Global Health Policy
The IARC’s reclassification has sent ripples through the medical community. While the World Health Organization (WHO) has not yet updated its official guidelines on contraceptive use, experts anticipate that regulatory bodies—including the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA)—will soon revisit labeling requirements. As of May 2026, no major health authority has recommended discontinuing combined hormonal contraceptives, but many are urging:
- Stronger informed consent processes, ensuring women understand the breast cancer risks alongside benefits.
- Expanded access to non-hormonal alternatives, particularly in regions where combined pills are the primary method.
- Enhanced screening protocols for women on long-term hormonal contraception, especially those with risk factors.
The American Cancer Society and the European Society for Medical Oncology (ESMO) have issued statements emphasizing that the IARC’s classification does not mean women should stop using contraception. Instead, they advocate for personalized risk assessments, where women and their healthcare providers weigh individual risk factors against reproductive goals.
@WHO statement on IARC’s classification of hormonal contraceptives:
“The benefits of contraception in preventing unintended pregnancies and reducing cancer risks (e.g., ovarian, endometrial) remain substantial. Women should discuss options with their healthcare providers.”
What Should Women Do Now? Expert Recommendations
If you’re currently using a combined hormonal contraceptive and have concerns, here’s what leading oncologists and gynecologists recommend:
- Schedule a risk assessment: Consult your doctor to evaluate your personal and family history of breast cancer, as well as other risk factors (e.g., obesity, alcohol consumption, dense breast tissue).
- Explore alternatives: If you’re at higher risk, ask about progestin-only pills, hormonal IUDs (if breast cancer-free), or non-hormonal methods like copper IUDs or barrier contraception.
- Monitor breast health: Perform monthly self-exams and adhere to recommended screening schedules. Women on long-term hormonal contraception may benefit from supplemental MRI screening if they have dense breasts or a family history.
- Stay informed: Follow updates from the American Cancer Society and the WHO for evolving guidelines.
For women diagnosed with breast cancer, the National Comprehensive Cancer Network (NCCN) guidelines already advise against hormonal contraception due to potential interactions with anti-estrogen therapies (e.g., tamoxifen). The IARC’s findings reinforce this stance but do not introduce new restrictions for this group.
The Road Ahead: What’s Next in Research?
The IARC’s 2024 report is not the final word. Ongoing studies, including the Million Women Study (UK) and the Nurses’ Health Study (USA), are refining our understanding of how different progestins and estrogen doses influence risk. Key questions remain:
- Do newer, low-dose combined pills carry a lower risk than older formulations?
- Can genetic testing identify women who are most susceptible to hormonal contraceptive-related breast cancer?
- Will non-hormonal contraceptives (e.g., the recently approved Qlaira alternative) become the new standard for high-risk women?
The next major checkpoint will be the WHO’s Global Contraception Summit in Geneva, scheduled for October 2026, where policymakers and scientists will discuss how to balance access with emerging safety data. Until then, the message remains clear: Informed choice is paramount. Women should partner with their healthcare providers to make decisions tailored to their unique health profiles.
As we navigate this evolving landscape, one thing is certain: The conversation around hormonal contraception and breast cancer risk is far from over. What is needed now is clearer communication, better data, and compassionate care—so that no woman has to choose between her reproductive health and her long-term well-being.
Dr. Helena Fischer is a physician and health journalist with an MD from Charité – Universitätsmedizin Berlin. She specializes in translating complex medical research into actionable insights for the public.
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