IUDs May Protect Against Cervical Cancer

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The IUD, or intrauterine device, is a highly effective method of birth control, and now a new study reveals that it may be useful in guarding against cervical cancer as well.

A research team from the Institut Català d’Oncologia in Barcelona, Spain, has found that women who used IUDs were about half as likely to develop cervical cancer as women who did not use the contraceptive devices. IUD users had a 44% lower risk of developing squamous-cell carcinoma and 54% lower risk of adenocarcinoma and adenosquamous carcinoma — all common forms of the disease.

Even the researchers were surprised by the findings. “The data (available) before we did this study were very inconsistent, so we didn’t expect to find such a strong association with this protective effect,” lead researcher Dr. Xavier Castellsagué told Reuters.

The study was based on data from 26 previous studies involving 20,000 women from 14 countries. The researchers found that while IUD use appeared to affect the risk of cervical cancer, it had no impact on women’s risk of contracting HPV, the virus that causes most cervical cancers. Rates of HPV were the same, whether women used an IUD or not.

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Researchers speculated that there may be something about the IUD that prevents HPV from triggering cancer. Reported USA Today:

By causing a chronic, low-level irritation in the cervix, an IUD may rev up a woman’s immune system, as if her body were trying to heal a wound, according to an accompanying editorial by Karl Ulrich Petry, a researcher at the Klinikum Wolfsburg in Germany. That small immune boost may be enough to clear persistent HPV infections and even get rid of precancerous lesions.

IUDs are small, plastic T-shaped devices that are inserted into the uterus. There are two types available in the U.S.: one uses copper, which is toxic to sperm, as a contraceptive; the other releases progestin, a synthetic version of the hormone progesterone, to prevent pregnancy.

The IUD is known for being low cost and highly effective, and because the device can stay in place for up to 10 years, it is a low-maintenance contraceptive choice. But there’s no reason that women who are worried about cervical cancer should have an IUD inserted.

For one, the new study shows only an association between IUD use and lower risk of cancer; it does not prove that IUDs directly cause cancer prevention. More research is needed to confirm the benefit. Further, there are other effective ways already available to prevent cervical cancer, including the HPV vaccine, HPV testing and routine Pap tests.

The new research appeared in The Lancet.

MORE: IUDs to Treat Endometrial Cancer and Preserve Fertility in Young Women

Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.