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Research shows both increased risks for some cancers and protective effects for others. The overall balance often leans neutral or even beneficial for long-term cancer risk in many users, though individual factors like duration of use, age, and specific formulation matter.
Increased Cancer Risks Associated with Hormonal Birth Control
Hormonal contraceptives are linked to modest increases in risk for certain cancers, particularly during current or recent use. These risks typically decline after stopping.
- Breast cancer — Current or recent use is associated with a small increased risk (around 20-30% relative increase in many studies). For example, a large analysis found a relative risk of about 1.20 for current/recent users compared to never-users. This risk rises with longer duration of use and returns to baseline within about 5-10 years after stopping. Recent 2025 studies highlight variations by progestin type, with some (like desogestrel) linked to higher risks than others (like levonorgestrel). Absolute risk remains low in younger women due to the rarity of breast cancer in premenopausal ages (e.g., roughly 13 extra cases per 100,000 women per year in some cohorts).
- Cervical cancer — Longer use increases risk, partly due to hormonal effects and potential interactions with HPV (the main cause). Risk may rise by about 10% or more with extended use, though this is influenced by screening and HPV status.
- Liver cancer — Rare associations exist with long-term use (e.g., hepatocellular carcinoma in some older data), but recent reviews suggest limited or no strong link in modern formulations.
Protective Effects Against Certain Cancers
Hormonal birth control often reduces risk for several cancers, with benefits persisting long after discontinuation.
- Ovarian cancer — Use reduces risk by about 30-50%, with greater protection from longer duration. This effect lasts for many years post-use.
- Endometrial cancer — Similar strong protection (around 30-50% reduction), especially with prolonged use, persisting decades after stopping.
- Colorectal cancer — Evidence shows a modest reduction (around 15-20% lower risk in meta-analyses), though not all studies agree on duration effects.
Overall lifetime cancer balance in past users is often neutral, with increased risks for breast and cervical cancers offset by reductions in ovarian, endometrial, and colorectal cancers.
Key Considerations
- Progestin-only methods (e.g., mini-pill, implants, IUDs like Mirena, injections) show similar patterns to combined pills for breast cancer risk in recent data — a small increase during/recent use — but may offer comparable protective effects for gynecological cancers.
- Risks are generally small in absolute terms, especially for younger users, and must be weighed against benefits like pregnancy prevention (which carries its own risks) and non-cancer advantages (e.g., reduced ovarian cysts, lighter periods).
- The International Agency for Research on Cancer (IARC) classifies combined estrogen-progestogen contraceptives as Group 1 carcinogens (carcinogenic to humans) based on evidence for breast, cervical, and liver cancers, but also notes protective effects.
Sources:
- National Cancer Institute (NCI): Oral Contraceptives and Cancer Risk (updated overview of observational studies showing increased breast/cervical risks and decreased ovarian/endometrial/colorectal risks).
- American Cancer Society: Birth Control & Cancer overview (2025 update on methods raising/lowering risks).
- Collaborative Group analyses and meta-analyses (e.g., on breast cancer relative risks ~1.20 for recent use).
- Recent cohort studies (e.g., Swedish 2025 data on formulation-specific breast cancer risks; UK nested case-control and meta-analysis on progestogen-only methods).
- IARC Monographs on combined hormonal contraceptives (Group 1 classification with balanced evidence).
