Researchers at Oxford University have found that certain birth control pills increase the risk of breast cancer by up to 30 percent.
The study’s findings were published in PLOS Medicine on Tuesday.
“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 study states.
In their conclusion, the researchers wrote that “progestagen-only contraceptives is associated with a slight increase in breast cancer risk, which does not appear to vary by mode of delivery, and is similar in magnitude to that associated with combined hormonal contraceptives.”
“When our findings for oral contraceptives are combined with results from previous studies (which included women in a wider age range), they suggest that the 15-year absolute excess risk of breast cancer associated with use of oral contraceptives ranges from 8 per 100,000 users (an increase in incidence from 0.084% to 0.093%) for use from age 16 to 20 to about 265 per 100,000 users (from 2.0% to 2.2%) for use from age 35 to 39,” the study says.
According to their findings, the risk of breast cancer gradually decreases once the woman stops using it.
Instead of discouraging the use of birth control because of the findings, the researchers wrote that “excess risks must be viewed in the context of the well-established benefits of contraceptive use in women’s reproductive years.”
Claire Knight of Cancer Research UK, which funded the study, told the Guardian that this risk was “small” and “should not discourage most people from taking the pill.”
“Women who are most likely to be using contraception are under the age of 50, where the risk of breast cancer is even lower,” Knight said. “For anyone looking to lower their cancer risk, not smoking, eating a healthy balanced diet, drinking less alcohol, and keeping a healthy weight will have the most impact.”
Knight continued, “there are lots of possible benefits to using contraception, as well as other risks not related to cancer. That’s why deciding to take them is a personal choice and should be done after speaking to your doctor so you can make a decision that is right for you.”
The study was based on data from 9,498 women who developed invasive breast cancer between ages 20 to 49 and 18,171 closely matched women without breast cancer.