Hormonal contraceptives, such as the pill or IUDs, contain a combination of estrogen and progesterone or progesterone only. They prevent pregnancy by blocking the release of eggs from the ovaries, thinning the lining of the uterus, or thickening the mucus in the cervix to help keep sperm from reaching the egg. These forms of contraception are effective, but do they put a woman at a higher risk for breast cancer?
A University of Oxford study finds the answer is “yes,” particularly among women using progesterone-only contraceptives. “Our findings suggest that there is a relative increase of around 20% to 30% in breast cancer risk associated with current or recent use of either combined oral or progestagen-only contraceptives,” the researchers write. There was a slight increase in breast cancer risk regardless of how the hormonal contraception is delivered — whether by pill, implant, intrauterine device, vaginal ring or patch.
The study analyzed data on nearly 9,500 women under the age of 50 who had received a breast cancer diagnosis between 1996-2017, and over 18,000 closely matched controls without cancer. All the women were part of a UK primary care database, the “Clinical Practice Research Datalink” (CPRD).
Age mattered. Breast cancer risk was higher among women using hormonal contraception who were over 35.
A woman's age while using hormonal contraception also mattered. Breast cancer risk was higher among women using hormonal contraception who were over 35. With 5 years use of either oral combined or progesterone-only contraceptives, the incidence of breast cancer during 15 years was estimated at 8 cases per 100,000 users at age 16-20 years. However, among users who were between 35 and 39 years years old, the number of cases per 100,000 users rose to 265.
“Given that the underlying risk of breast cancer increases with advancing age, the absolute excess risk associated with use of either type of oral contraceptive will be smaller in women who use it at younger rather than at older ages,&rdquo: the authors write, adding, “Such risks need be balanced against the benefits of using contraceptives during the childbearing years.”
Choosing the right birth control plan can be challenging. It’s always a good idea to discuss options with your healthcare provider when making a decision. Meanwhile, medical experts agree there are lifestyle options that may reduce your risk of developing breast cancer, such as:
- Keeping a healthy weight
- Being physically active
- Choosing not to drink alcohol or drink alcohol in moderation
The study is published in PLOS Medicine.