More than 10 million American women use birth control pills. They are the go-to contraceptive not only for pregnancy prevention, but also for PMS symptoms, heavy periods, and acne. Previous studies have suggested that birth control pills increase breast cancer risk, and the most recent research strengthens this relationship.

Birth Control Pills: A Known Carcinogen

Birth control pills join tobacco, asbestos, plutonium, and diesel exhaust as a group 1 carcinogen according to the World Health Organization. This means birth control pills are “a known and probable cancer-causing agent to humans.”

The latest study published in the August 2014 edition of the journal Cancer Research confirms the finding of past birth control/cancer studies. Researchers studied 1,102 women with breast cancer, along with 21,952 controls, and found that recent oral contraceptive use—particularly high-dose estrogen birth control pills—increased breast cancer risk by more than 50%. Birth control pills with ethynodiol diacetate (a type of progestin) also raised breast cancer risk by more than double, while triphasic birth control pills (pills that deliver different hormone doses over three stages of the monthly cycle) more than tripled breast cancer risk! Not all birth control pills fared so badly, however. Low-dose estrogen birth control pills did not seem to increase breast cancer risk.

Birth control pills block pregnancy by delivering a mix of estrogen and progestin hormones to your body. But these same hormones also over-stimulate breast cancer cells, which increases breast cancer risk. Dr. Angela Lanfranchi writes in her booklet on Breast Cancer Risks and Prevention:

“Estrogen can cause cancers in two ways. First, estrogen acts as a “mitogen.” Estrogen stimulates your breast tissue to increase cell divisions (mitoses). This sometimes results in cancers due to errors in cell division (mutations). Second, certain metabolites of estrogen also act as carcinogen or genotoxins, by directly damaging DNA, thereby causing cancer cells to form.”

Your risk for breast cancer further increases if you have a strong family history of breast cancer, you or a family member have had a biopsy that showed abnormal cells, or you carry an abnormal breast cancer gene.

If you are currently taking birth control pills, consider a safer method of contraception, such as the use of a diaphragm and/or condom. If you insist on taking birth control pills, then make sure you are on a low-dose estrogen pill.