Women who have used an IUD may have a 30% lower risk of invasive cervical cancer than women who have not.

Intrauterine devices (IUDs) are a safe and long-acting way to prevent pregnancy — but new evidence shows that they may also lower the risk of cervical cancer.

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The findings are from a new report published this week in Obstetrics & Gynecology in which researchers analyzed IUDs and cervical cancer risk in over 12,000 women worldwide.

"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.

IUDs are small, T-shaped devices that are placed in the uterus to prevent sperm from reaching an egg. They are a highly effective form of birth control and they can offer protection against pregnancy for up to three, five, or ten years.

The study is the first of its kind to combine and analyze data from multiple studies to look at the issue. "We went through all of the relevant human epidemiological data on this topic and narrowed it down to 16 high-quality observational studies of over 12,000 women from all over the world," Cortessis says.

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The research suggests that invasive cervical cancer may be approximately one-third (30%) less frequent in women who have used the IUD compared with women who have not.

There are two types of IUDs: hormonal and nonhormonal. The hormonal IUD releases the synthetic hormone progestin, which changes the cervical mucus to block sperm from getting into the uterus — and it can also prevent ovulation. The non-hormonal or copper IUD (ParaGard), continuously releases copper into the uterus, causing an inflammatory reaction that makes it difficult for sperm to move and reach the egg.

The researchers weren’t sure about the type of IUD used and the age of the women when they started using them. However, Cortessis says that most of the studies represent the use of copper IUDs because they were completed before the hormonal IUD was available. "These are observational studies, so we're always a bit skeptical and there's still so much more data that needs to be collected and analyzed," Cortessis says.

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Cervical cancer is the third most common cancer among women worldwide — and rates are steadily growing, mostly in developing countries.

According to the World Health Organization (WHO), approximately 528,000 women were diagnosed with cervical cancer worldwide in 2012, and 266,000 women died from the disease. By 2035, the WHO projects that those numbers will climb to more than 756,000 and 416,000, respectively.

The most important risk factor for cervical cancer is infection with the human papillomavirus (HPV), which is spread through sexual activity. "It's a common infection and in about 90% of women who have HPV, their body will clear the virus on its own but in 10% of women, the infections don't clear up and they can turn into cervical cancer," Cortessis says.

Cervical cancer rates are declining in the United States, due to greater use of the HPV vaccine and access to screening technology. “But there are still epidemics going on in most parts of the world where women don’t have regular access to screenings — those ladies stand to benefit most from this," Cortessis says. Because the studies included women who had IUDs before the HPV vaccine was widely available, Cortessis says, these findings could be most important for women who are unvaccinated, over 30 years old, and live in low-resource countries.

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"The possibility that a woman can choose a contraceptive method that also offers some protection against cervical cancer could be very impactful," Cortessis says.

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 this hypothesis is correct, it could reduce the need for costly and sometimes invasive procedures to remove precancerous cervical lesions. "If the IUD stimulates the body to mount an immune response that clears precancerous lesions, this seems much more desirable for a woman than getting a positive screening followed by surgical removal of lesions," Cortessis says.

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Does this mean you should get an IUD to protect against cervical cancer? Nope.

"Our summary is only as good as the data out there, and there's still much more research that needs to be done before we can say that the IUD prevents cervical cancer, or recommend the IUD as a protective measure," Cortessis says. As we mentioned before, the findings did not look at the type of IUD (hormonal or copper) or at which age it was inserted, which are two important factors.

So no, gynecologists probably won't be recommending IUDs to prevent cervical cancer anytime soon. However, these study findings are incredibly promising, Cortessis says, and shows the potential for IUDs to have more health benefits than simply providing protection against pregnancy.

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Right now, the best way to protect yourself against cervical cancer is to get the HPV vaccine before you're sexually active and do regular screenings.

You'll need to get vaccinated before you are sexually active, Cortessis says, so your body has time to develop a robust immune response before you are exposed to the virus. The HPV vaccine doesn't protect against all strains or types of HPV, but it does protect against the strains that commonly cause cancers. "In the US, the proportion of women who have gotten the vaccine is still very low and in the developing world, fewer than 2% of girls had been vaccinated — so we have a long way to go," Cortessis says.

"The biggest takeaway from this study is still that everybody should be screened for cervical cancer according to the current guidelines," Cortessis says. Today, that means women between the age of 21 and 65 should get pap smears every three years and HPV testing every five years. If you're considering getting an IUD, you should talk to your doctor about the possible risks and benefits and which type is the right choice for you.

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