Some Hormonal IUDs Increase Breast Cancer Risk

Women who use IUDs (intrauterine devices) with the hormone levonorgestrel for birth control have a 40% increased risk of breast cancer, but their overall risk of the disease remains low, a study has found. 

For a woman in her 30s living in the U.S., these findings mean that use of a levonorgestrel IUD could increase the risk of developing breast cancer from 1 in 204 (0.49%) to 1.4 in 204 (or 0.69%) over about a seven year period..

For people with a history of breast cancer, whether hormone receptor-positive or hormone receptor-negative, doctors recommend using birth control that doesn’t contain hormones.  

“Long-term use of extra hormones, in this case, a hormonal-based IUD device, is associated with an elevated risk of breast cancer,” said Marisa Weiss, MD, founder and chief medical officer of Breastcancer.org. “For women seeking effective long-term contraception, ask your doctor about a non-hormonal effective type of contraception, like a ParaGard IUD instead of a hormonal based IUD or use of birth control pills. For women diagnosed with breast cancer who have a hormonal form of contraception in place, ask your doctor to switch you over to a non-hormonal effective method of contraception. Also, beyond contraception, make sure that you protect yourself against sexually transmitted diseases as well.”

The study involved two groups of Danish women ages 15 to 49 — 78,595 women who used the IUD and 78,595 who didn’t use hormonal birth control — for about seven years. During this follow-up period, 1,617 of the women were diagnosed with breast cancer.

Among the women who used the IUD for up to five years, there were 14 more diagnoses of breast cancer for every 10,000 women. The risk didn’t increase if the women used the IUD for a longer time.

These findings aren’t the first to link hormonal birth control and breast cancer risk. Another study published in 2017 by the same researchers, compared breast cancer diagnoses in Danish women ages 15 to 49 who used any hormonal birth control with those who did not. They found hormonal birth control slightly increases the risk of breast cancer. But the importance of the increase is unique to each woman and depends on many factors, including age; general health; her personal risk of breast cancer; and other breast cancer risk factors, such as smoking cigarettes, drinking alcohol, and maintaining a healthy weight.

Other research has shown that the benefits of  hormonal birth control include a lower risk of ovarian, endometrial, and colon cancer. Because of protection against these cancers, overall cancer risk may be slightly lower in women who use hormonal birth control compared to women who don’t, even with the small increased breast cancer risk seen in this study.

According to 2017-2019 statistics from the Centers for Disease Control (the most recent stats available), about 10.4% of women ages 15 to 49 in the United States use an IUD or an implant for birth control. IUDs are inserted into the uterus by a doctor and last up to eight years. In the United States, levonorgestrel IUDs are sold under the brand names Mirena, Liletta, Kyleena, and Skyla.

“Given the increase in levonorgestrel IUD use among females at an age with some risk for breast cancer, and its likely long-term use, information about breast cancer risk should accompany discussions about benefits and risks,” the researchers concluded.

One possible limitation of the study was that it didn’t account for how often the women were screened for breast cancer. Women with an IUD might be more likely to visit a doctor and have breast cancer screening. The study also didn’t take into account whether some women may have had the IUD removed before the recommended date, which could lead to breast cancer risk being underestimated.

The study also does not address whether the increased breast cancer risk goes away once the hormonal IUD is removed.