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What You Need to Know About a New Study Linking Birth Control to Breast Cancer

We're talking about one additional case in every 7,700 women.

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Dec 6 2017, 11:34pm

Lars Klove/Getty Images

No doubt, headlines can be scary. So if you’re reading the news that women who used hormonal birth control had a 20 percent higher risk of breast cancer and are side-eying your pack of pills right about now, we’re here to offer some perspective.

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First, let’s get into the study, which was just published in the New England Journal of Medicine. Researchers followed 1.8 million Danish women ages 15 to 49 for nearly 11 years. The researchers tapped into the National Register of Medicinal Product Statistics for pharmacy records on filled birth control prescriptions. Then they consulted the Danish Cancer Registry for cases of breast cancer. In short, the two data points were compared and analyzed.

They found that women who’d recently used or currently use hormonal contraception were 20 percent more likely to have developed breast cancer than women who had never used it. Those who used it for less than a year were the least at risk (their odds rose nine percent), while those who used it for more than 10 years had the highest risk—they were 38 percent more likely to develop breast cancer. Even after stopping, the risk stayed elevated for at least five years.

Yikes. Though it’s not exactly clear why, it may be the estrogen or progesterone hormones present in these Rxs, though more research is needed to know exactly what’s going on.

This finding is consistent with past research, which has also found a 20 percent bump in breast cancer rates. What was telling about this study, however, was that they included newer forms of birth control, like the vaginal ring, patches, implants, injections, and hormonal IUD—as well as current pill formulations that are lower in estrogen than in decades past—giving a more complete and updated picture from earlier research.

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While a 20 percent jump sounds like lot (and it’s significant statistically as far as research goes), it’s not as alarming as you may think. As the authors noted, hormonal contraception can be blamed for causing one additional case of breast cancer for every 7,690 women using birth control every year. And we don't know what happened to these women, just that they were diagnosed.

Plus, hormonal birth control offers some very important health benefits. Pregnancy protection, for one. But in addition to that, the authors concluded: “This risk should be weighed against important benefits of hormonal contraceptives such as good contraceptive efficacy and reduced risks of ovarian, endometrial, and perhaps colorectal cancer (at least for combined oral contraceptives that were commonly used in the 1970s and 1980s).” Previous studies have shown that birth control cuts the risk of endometrial cancer in half and cuts risk of ovarian cancer by 27 percent.

An accompanying editorial by David J. Hunter, the director of the Harvard-Oxford program in epidemiology, also lends some insight. “First, the approximately 20 percent higher risk of breast cancer among women who currently use hormonal contraceptives and those who do not must be placed in the context of the low incidence rates of breast cancer among younger women,” he writes. For women younger than age 35, the increase in risk from hormonal birth control is just an additional two out of every 100,000 women. Those are very low odds. He also points out that some research shows that using it for longer than five years has a net effect of reducing your total risk of cancer.

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Considering breast cancer likelihood rises with age—and the link between hormonal contraception and the disease gets stronger as women age—you may consider talking with your doctor about other methods of birth control as you get into your 40s, Hunter notes.

What is certain is that hormonal contraception is good for women’s health, according to the American Congress of Obstetricians and Gynecologists. When Tonic contacted ACOG about the new study, Chris Zahn, vice president of practice replied in an emailed statement: “Contraception is a medical necessity for women during approximately 30 years of their lives. 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. These methods offer women critical control over their health, including if and when to become pregnant, reducing risk of cervical cancer, and in some cases aiding with management of chronic conditions like acne or painful periods. As with any medical intervention, hormonal contraception is associated with specific health risks.”

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Zahn said ACOG takes the safety of contraception very seriously and reviews new research, but noted that there are several limitations of the paper. “While this study raises known associated risks between breast cancer and hormonal contraception, we believe a robust evaluation of the study, including the study design, is necessary to accurately interpret the findings and reach conclusions,” she wrote. “This should include consideration of other factors that have significant impact on the findings, including family history of breast cancer for both pre and post menopausal women, stage of disease, and morbidity or mortality from the breast cancer diagnoses.”

If you’re concerned, you should talk to your doctor to weigh the benefits and risks of your choice in birth control, Zahn says. If you have certain medical conditions, like high blood pressure, a personal history of breast cancer, or you’re a smoker over age 35, hormonal contraception may not be the right choice for you, says ACOG. (Interestingly, ACOG says women with BRCA gene mutations benefit from taking the pill because it lowers their ovarian cancer risk.) But that’s a chat to have with your doctor. They’re there to help you make the right choice for your health.

Read This Next: It’s Way Too Early to Say IUDs Reduce the Risk of Cervical Cancer

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