Many individuals wonder about the potential link between birth control and serious conditions like brain tumors. This article provides an evidence-based overview of what current research indicates about hormonal contraception and brain tumor risk.
Understanding Hormonal Birth Control
Hormonal birth control methods introduce synthetic hormones, primarily estrogen and/or progestin, into the body to prevent pregnancy. Common forms include oral contraceptive pills, hormonal intrauterine devices (IUDs), implants, and injections.
Combined hormonal methods contain both estrogen and progestin, while progestin-only methods contain only progestin. These hormones primarily prevent ovulation, thicken cervical mucus, and thin the uterine lining to prevent implantation.
Exploring the Scientific Evidence
Research on hormonal birth control and brain tumors primarily focuses on meningiomas and gliomas. For most brain tumor types, studies indicate no significant increased risk with hormonal birth control use.
However, some studies have identified a specific, albeit small, association between certain progestogen-only hormonal birth control methods and meningioma. Meningiomas are typically slow-growing tumors that form in the protective layers around the brain and spinal cord, and they are usually non-cancerous. A large study from France, published in 2024, found that prolonged use (over a year) of specific progestogens like medrogestone, medroxyprogesterone acetate (found in the Depo-Provera injection), and promegestone was linked to an increased risk of intracranial meningioma requiring surgery. For example, medroxyprogesterone acetate was associated with a 5.6-fold increased risk with prolonged use.
Desogestrel, found in some oral contraceptive pills, has also been linked to a small increase in meningioma risk with long-term use (five years or more). Conversely, other widely used progestogens, such as progesterone, dydrogesterone, and levonorgestrel (often found in hormonal IUDs), have shown no excess risk of meningioma. This suggests that the association is not with all progestogens but rather with particular types and duration of use.
Regarding gliomas, a rarer brain tumor type, one Danish study observed a possible increased risk with long-term hormonal contraceptive use, especially progestin-only formulations. This study noted a 90% relative increased risk for those using hormonal contraceptives for over five years. However, the overall incidence of glioma remains very low, meaning even an increased relative risk translates to a small absolute risk.
Interpreting Research Findings
Understanding these findings requires distinguishing between correlation and causation. Observational studies identify associations between factors like birth control use and health outcomes, but they cannot definitively prove direct causation, as other influencing factors might be involved.
When studies report an increased risk, it is important to consider “absolute risk” versus “relative risk.” While some studies indicate a higher relative risk for specific tumors, the absolute chance of developing a brain tumor due to birth control remains extremely low. For instance, even a five-fold increase in risk for a rare condition like meningioma (e.g., four in every thousand women by age 80) still means a small number of additional cases.
For desogestrel, one estimate suggests that among women using it continuously for over five years, approximately 1 in 17,331 might develop a meningioma requiring surgery. Limitations of these studies often include the inability to account for all potential confounding factors, such as genetic predispositions or other lifestyle elements.
Making Informed Health Choices
Making informed health decisions about birth control involves a personalized approach. Discuss any concerns and your health history with a healthcare provider. They can assess your specific risk factors and benefits of different birth control methods.
Your doctor can provide tailored advice based on your medical background, lifestyle, and preferences. For most individuals, hormonal birth control remains a safe and effective option for pregnancy prevention and managing various health conditions. Regular check-ups and open communication with your healthcare provider are important.