Since the 1960s, when the birth control pill made its debut, contraceptives have played a major role in family planning. So when researchers discovered that women taking hormone-based birth control had a higher incidence of breast cancer, making the contraceptives safer became an important public health priority. Many experts believed they found a solution in options with far lower doses of estrogen, a hormone long linked to breast cancer occurrence. But a new study suggests that low-dose contraceptives have not had the impact doctors expected, and experts are urging women to talk to their doctors about the implications for their breast health, even though the overall risk remains relatively small.

The study, published in December in The New England Journal of Medicine, followed 1.8 million women for an average of about 11 years, finding that those on hormonal contraception had a 20 percent higher risk of breast cancer—no matter the dose of estrogen—than women who never used those birth control methods. It’s an important discovery, especially with an estimated 140 million women across the globe using some form of hormonal contraception. Now, the findings have experts taking a closer look at another hormone singled out by the study: progestin.

Hormonal birth control methods, which include pills, patches, shots, and vaginal rings or intrauterine devices, prevent pregnancy by delivering combinations of synthetic estrogen and progestin, or just progestin alone, into the body. Estrogen and progestin stop the ovaries from releasing eggs, thicken the cervical mucus to keep sperm from entering the uterus, and thin the lining of the uterus to prevent implantation. Because high estrogen levels may cause certain types of cancer cells to grow, experts have long believed estrogen was the main hormonal culprit linking the contraceptives to an increased breast cancer risk, says Justin Chura, MD, Chief of Surgery and Director of Gynecologic Oncology and Robotic Surgery at our hospital near Philadelphia.

“ Now we see that the progestin plays a role, as well in the risk. We definitely had a faulty assumption going in.” – Justin Chura, MD – Chief of Surgery and Director of Gynecologic Oncology

There’s no reason for panic, Dr. Chura says, since the risk of breast cancer from hormonal contraception remains relatively small for most women. “Oral contraceptives are still a great class of drugs,” he says. “There is no ‘free lunch’ in terms of any of the medications we prescribe. There are always risks and benefits.” Such risks for hormonal contraception include blood clots, strokes and heart attacks. Benefits typically include a reduced risk of other types of cancer, including ovarian and endometrial cancers, as well as lighter or more regulated menstrual cycles, and, of course, help with family planning.

But each woman should weigh her individual risks, Dr. Chura says. Because breast cancer risk increases with both age and the length of time hormonal contraceptives are used, women already at higher risk for breast cancer, and those who are older and no longer planning to have children, may want to consider switching to a hormone-free birth control method, such as a diaphragm or condoms. Older women who have been on hormone-based birth control for a number of years may also consider getting screened for breast cancer at the earliest age that guidelines recommend. And women who are on progestin-only contraception may consider talking to their doctor about changing their birth control method.

For women in their 20s, the benefits of hormonal contraception often outweigh the risks, but medical and family histories still come into play. “Even if you’re 25, if you’re a BRCA mutation carrier, it makes sense for you to factor in the breast cancer risk that comes with hormonal contraception because you’re already at a higher risk for breast cancer than people without that mutation,” Dr. Chura says. Oral contraceptives, though, are also known to decrease the risk of ovarian cancer for patients with and without a BRCA mutation.

Despite the new findings, Dr. Chura says women should talk to their doctor before making any changes to their birth control. “Now women can have more educated discussions with their doctors,” he says.