Birth Control Pills and Cancer Risk
Birth control pills (BCPs) were first introduced in the 1960s and are the most commonly used method of contraception in the United States. Since their introduction, BCPs have undergone significant changes in their make-up and the doses women take. For instance, early BCPs contained 150 micrograms of ethinyl estradiol, whereas today’s BCPs contain an average of 20 micrograms. This continuing evolution makes it hard to apply the results of previous studies looking at cancer risk to today’s BCP preparations. There have been a few more recent studies that can provide some guidance.
Studies have fairly consistently found a small increase in breast cancer risk for women who use BCPs (estimated to be between 7-20% in different studies). The increase in risk is strongest in women over 40 years of age. Breast cancer risk is also a little higher when BCPs are used for longer periods of time. In all of the studies, the risk was found to go down after a woman stops taking BCPs. One study found that 10 years after stopping BCPs, there was no increased risk of breast cancer over women who had not used BCPs.
Women who take BCPs for 5 years or more are at an increased risk of cervical cancer and this risk increases as BCPs are used for longer periods of time. As with breast cancer, the risk goes back down, over time, after BCPs are stopped.
The risk of endometrial cancer is lower among women who have taken BCPs. Some studies estimate the risk to be 30% lower and that number increases as BCPs are used for longer periods of time. This lower risk lasted for many years after stopping BCPs.
The risk of ovarian cancer is estimated to be 30-50% lower in women who have taken BCPs. The risk continues to decrease the longer a woman takes BCPs. This lower risk is still seen up to 30 years after stopping BCPs.
Studies have found a lower risk of colorectal cancer in women who use BCPs.
What can I do with all this information?
Always have a discussion with your healthcare provider about the risks and benefits of any medication you are considering taking. In the case of BCPs, it is important for your provider to consider your personal and family history before prescribing BCPs. Women already at higher breast cancer risk, such as those with a strong family history, genetic mutations, or those with other health concerns (such as blood clots) should consider other options for birth control. Non-hormonal birth control options do not have any effect on cancer risk. Your provider should inform you of all your options.
Women who took BCPs in the past should have cancer screening tests for breast and cervical cancers that are recommended for all women their age. They do not require any additional testing.
Resources for more information
Oral Contraceptives and Cancer Risk from the NCI.
Do Hormonal Contraceptives Increase Breast Cancer Risk? From BreastCancer.org.
Birth Control & Cancer: Which Methods Raise, Lower Risk? From the American Cancer Society.