A study conducted in Denmark has found that even low doses of hormones in contraceptive pills, intrauterine devices (IUDs), implants, and injections, still have potential to heighten the risk of breast cancer.

Of the nearly 1.8 million women who participated in the decade-long study, over 11,500 of those women developed breast cancer, still the most common form of cancer in women across the globe.

The findings specified the hormone progestin, the primary component in some birth control pills and many IUDs, as the cause for a 21 percent increase in breast cancer risk. It’s also important to consider that IUDs release hormones directly to the uterus, rather than traveling through the bloodstream with pills or injections.

The increase in risk may also correlate with the length of time a woman has been taking contraception. Participants who used contraception with normal hormone levels for more than ten years saw the highest increase in risk. Those who used hormones for five years still saw an increased cancer risk, despite discontinued use.

While it’s been decades since the first links between birth control and breast cancer were established, other studies have shown a decreased risk of ovarian, endometrial, or even colorectal cancers.

Dr. Hal Lawrence, an obstetrician-gynecologist and chief executive officer of the American College of Obstetricians and Gynecologists, is careful to scare women away from contraception that might help beyond preventing unwanted pregnancies. He said, “We’re never going to eliminate all the potential risks that come with medication, but we know a lot of the benefits, and the number one benefit is preventing unintended pregnancies and the health and socio-economic risks that go along with that.”

If you are sexually active, you should already be using condoms. But if you need to take contraception, speak with your doctor and get to know your body’s tolerance for hormones. Overall health does change with age, as do potential risks, so it’s worth reassessing whether or not hormones will work for you.