Like anything else in the world, our choices are not without risk.
Taking birth control pills is no exception.
I recently had a friend ask me to discuss the risk of cancer with birth control pill use. She is taking the pill and after seeing my post about stopping, she reached out saying she's a little nervous to be taking them.
The risks we frequently hear about, and what I was trained to consider before prescribing, are these: heart attack, stroke, blood clot in leg or lungs, hypertension, liver or kidney dysfunction, breast cancer.
Many of these are related to the vascular, or blood vessel, system. For example, If someone is over the age of 35 and smokes, birth control pills are contraindicated due to the vascular risk. Throughout my years in training, there’s been a pendulum of controversy regarding birth control pills and their effect on cancer risk.
From risks flow contraindications, or reasons why something should not be prescribed.
In the case of birth control pills, namely estrogen-containing pills but progesterone-only may also confer risk, contraindications include:
history of heart attack, stroke, or VTE (Venous ThromboEmbolism, or blood clot in the leg or lungs)
uncontrolled hypertension
liver or kidney disease
history of breast cancer
The cancer risk associated with birth control pills is a very difficult thing to study. Cancer is not acute, it develops over a period of time. Birth control pill use changes over a woman’s lifetime and can be years or decades of use. The formulation of birth control pills varies from person to person and even within the same person. Other changes in a woman’s reproductive years are confounding factors (pregnancies, pregnancy outcomes, breastfeeding).
I found a meta-analysis (a study pooling the results of a bunch of other studies) published in 2013. It was sponsored by the Agency for Healthcare Research and Quality as well as the Centers for Disease Control and Prevention. It’s assessing “ever” versus “never” use of oral contraceptives and their associated cancer risks.
This is a summary of their findings:
Outcome | Birth Control Effect | Evidence Quality | Notes |
Breast Cancer | Increased | Moderate | More recent use of birth control pills was associated with higher risk |
Uterine Cancer (Endometrial) | Decreased | Moderate | |
Ovarian Cancer | Decreased | ||
Cervical Cancer | Increased | Poor | Studies aren’t great but there does seem to be an association, particularly among already HPV positive women |
Colorectal Cancer | Decreased | Moderate |
For all of these, I have to wonder why?
The leading theory as to the cause of ovarian cancer is an increased number of ovulation cycles in a woman’s reproductive life. This means that earlier puberty and later menopause, lack of pregnancy and breastfeeding are risk factors. This also fits with why birth control pills decrease the risk of ovarian cancer because they halt ovulation. Since this etiology of ovarian cancer remains a theory, the relationship with birth control pills also remains theoretical.
For endometrial cancer, my clinician brain wants to consider root causes and why birth control pills may decrease risk. Endometrial cancer is known to increase with obesity and polycystic ovary syndrome (among other things like hypertension, diabetes, age). In regards to obesity and polycystic ovary syndrome, birth control pills typically result in a regulated menstrual cycle as opposed to the hormonal dysregulation. Are the birth control pills helping in and of themselves, or are they helping to steady the hormonal imbalances of those diseases?
For cervical cancer, though the evidence was poor, the increased risk was found in already HPV-positive women with a higher association than non-HPV positive women. HPV stands for Human Papilloma Virus, a ubiquitous virus contracted with sexual activity, some strains of which are cancer-causing. Why would birth control pills affect this population more? Are the birth control pills affecting the immune system, allowing the HPV to progress to cancer with less resistance?
I’m sure very astute scientists are working on these very questions and looking for answers and I applaud them.
In another recent post, I shared my reasons for stopping birth control pills. It may not be the time for everyone to stop and it also may not be the time for everyone to start. This is an individual decision with a lot of risks and benefits to consider.
Everything we do, as doctors and as humans, is an assessment of risks versus benefits. If benefits generally outweigh the risks, we proceed. Think about this. Every time we get in a car we assume risk. We also assume that the benefit of getting to our destination is greater than the risk during transport. That’s what makes us get in the car. Health decisions are no different but there’s a heightened awareness of the good and the bad.
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Some of the information contained in this article is the result of my training, medical knowledge, and personal experience without a specific source to be cited.
This is not medical advice.
Jennifer M. Gierisch, Remy R. Coeytaux, Rachel Peragallo Urrutia, Laura J. Havrilesky, Patricia G. Moorman, William J. Lowery, Michaela Dinan, Amanda J. McBroom, Vic Hasselblad, Gillian D. Sanders, Evan R. Myers; Oral Contraceptive Use and Risk of Breast, Cervical, Colorectal, and Endometrial Cancers: A Systematic Review. Cancer Epidemiol Biomarkers Prev 1 November 2013; 22 (11): 1931–1943. https://doi.org/10.1158/1055-9965.EPI-13-0298