Study links breast cancer to birth control — here's what you need to know

Jennifer Gerson Uffalussy
Contributing Writer

A new study from Denmark published in the New England Journal of Medicine is making news because of its conclusion that the risk of breast cancer was higher among women who currently or recently used hormonal contraception (namely, birth control pills and hormonal intrauterine devices, or IUDs) than among those who had never used hormonal contraception. Per the study, risk was also found to increase with longer periods of use.

It’s the kind of news that might make some women want to toss their birth control pills in the trash — but before you do that, it’s important to understand the parameters and results of this new research.

First, it’s important to note that the study — which looked at 1.8 million Danish women over a decade — found that the absolute increases in breast cancer risk detected in this research were still incredibly small, translating to an incidence of 13 more cases of breast cancer a year per 100,000 women. In other words, for every 100,000 women using hormonal contraception, 68 could expect to be diagnosed with breast cancer, as opposed to 55 of those who were not using hormonal contraception.

A new study has brought new information to light about birth control pills. (Photo: Getty Images)

Secondly, the study was also limited by the fact that the study did not control for factors like level of physical activity, breastfeeding, and alcohol consumption, all of which have been found to influence breast cancer rates in varying ways. In other words, though more cases of breast cancer were identified among the group of women taking hormonal contraceptives, it is unclear what other factors might have also been at play in the cases in which diagnoses were made.

Women’s health experts say that this study does not invalidate the fact that quality contraception is a medical necessity for women.

Tracey Wilkinson MD, is an assistant professor of pediatrics at the Indiana University School of Medicine and a fellow of Physicians for Reproductive Health. She explains that this new study should not prompt women to abandon hormonal birth control.

“I never look at a large database study and apply it to just one patient,” Wilkinson tells Yahoo Lifestyle. “Every patient is unique and has different unique factors that impact their breast cancer risk rate — smoking, whether they choose to breastfeed, family history, race, ethnicity.”

She points out that not only does hormonal birth control protect against a lot of cancers —uterine, ovarian, and colon cancer, for example — but that this study also detected very few breast cancer events related to use of progestin-only forms of hormonal birth control, like the Depo-Provera shot, implants, and IUDs, the forms of hormonal contraception that are proven to be most effective.

Wilkinson also makes clear that there are major risks to women who are forced to deal with an unintended pregnancy — something that hormonal birth control does an excellent job of protecting against. So in evaluating the risks, a patient and provider need to work together for a holistic view.

“I always counsel young women to use contraception so that all pregnancies are planned ones and that you and your partner are ready for that pregnancy,” she says. “I don’t look at this study and get scared. I look at this study and think about how important birth control is, and how important it is that my patients, and all patients, have access to all forms of birth control.”

The question of birth control access is something now at risk for many American women in light of the Trump administration’s rollback of the contraception mandate of the Affordable Care Act (ACA), which guaranteed that all forms of FDA-approved birth control be covered with no co-pay for all insured Americans.

“Now the conversations I’m having with my patients are no longer about what method is most effective for them, but what method they can afford, that their insurance will cover,” Wilkinson says. That, she adds, is a real — and well-documented — threat to women’s health.

Dr. Chris Zahn, vice president of practice for the American College of Obstetricians and Gynecologists (ACOG), makes clear that he would caution women to reject certain methods of contraception solely based on these new Danish findings.

In a statement, Zahn notes, “For many women, hormonal contraception  the pill, the patch, the ring, IUDs, and the implant — is among the most safe, effective, and accessible options available.”

Zahn notes that these methods not only offer women, “critical control over their health, including if and when to become pregnant,” but have also been documented to reduce the risk of cervical cancer and are effective treatment options for chronic conditions ranging from acne to endometriosis.

Furthermore, Zahn emphasizes that the “safety of contraception is of critical concern” to ACOG, which takes this new research “very seriously.” The group also believes that “a robust evaluation of the study, including the study design, is necessary to accurately interpret the findings and reach conclusions. This should include consideration of other factors that have significant impact on the findings, including family history of breast cancer for both pre- and postmenopausal women, stage of disease, and morbidity or mortality from the breast cancer diagnosis.”

He continues, “Likewise, as the primary purpose of contraception is to prevent pregnancy, it’s vital that the study compare outcomes for women using hormonal contraception to outcomes for pregnant women,” in order to create a complete picture of the risks attendant on both eventualities. He says this is particularly useful in recognizing that in some instances, “hormonal contraception, risks and all, may be essential to preventing pregnancy in women with high-risk co-morbidities.”

Ultimately, Zahn says that the best thing for patients feeling concerned about these new findings is to speak with their own provider to “help them make informed decisions that weigh both the risks of pregnancy and the risks associated with hormonal contraception.”

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