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A rigorous assessment of 12,000 women worldwide has, for the first time, concluded that IUDs lower the risk of cervical cancer by 30%.

The research, which amassed epidemiological data from 16 separate studies, was

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“What we found was a very coherent pattern of less cervical cancer among people who’ve used the IUD based on thousands of women—and the pattern wasn’t subtle at all, it was stunning,” Dr. Victoria Cortessis , the study’s lead author and associate professor of clinical preventive medicine at the Keck School of Medicine at the University of Southern California, told BuzzFeed Health.

published in the journal Obstetrics & Gynecology. Here’s Caroline Kee, reporting for BuzzFeed News:

IUDs are T-shaped devices placed in the uterus to prevent pregnancy. Hormonal IUDs became available more recently than non-hormonal IUDs, which is why Cortessis and her colleagues believe most women represented in the 16 studies they looked at have non-hormonal, or copper, IUDs—which release copper into the uterus, causing an inflammatory reaction that blocks sperm from reaching the egg.

Cervical cancer is the third-most common cancer among women globally, and the World Health Organization estimates that by 2035, 756,000 people will be diagnosed with cervical cancer annually. In the United States, though, cervical cancer rates are declining due to the availability of the HPV (human papillomavirus) vaccine. Women in developing countries, on the other hand, are more at risk—and they also have less access to cancer screenings. Cortessis says these findings could be particularly helpful for those women in that it could offer an alternative route to cancer prevention.

But how exactly do IUDs decrease cancer risk? Here’s Kee again:

It’s not clear exactly why IUDs might lower the risk of cervical cancer. The current hypothesis is that IUDs might help the body clear persistent HPV infections, which are the most dangerous types when it comes to cervical cancer. “We do know that when the IUD is placed, that tissue has to be manipulated and this could cause an immune response in the same area of the cervix (called the transformation zone) where pre-invasive lesions arise and turn into cervical cancer,” Cortessis says. However, more research needs to be done to confirm if any of these mechanisms are actually responsible.

If IUDs cause the body to purge precancerous lesions, that’s a huge benefit—though it doesn’t mean you should run out to get an IUD solely as protection against cancer. The research still isn’t clear, and some factors (like the age at which an IUD is inserted) have yet to be fully analyzed. Still, the study is promising, and it underscores the need for increased healthcare options in the developing world.