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Dear Doctor: I'm too old (almost 30) for the HPV vaccination that can reduce my risk of cervical cancer. But I read that an IUD could do the same thing. Should I think about getting one, even though I prefer other forms of contraception?

Dear Reader: What a good question -- and a relevant one. Cervical cancer is the third most-common cancer among women worldwide. The majority of cases and deaths occur in countries with poor access to regular Pap smears; in the United States, where Pap smears are more readily available, the rates of cervical cancer and cervical cancer deaths are dramatically lower. Vaccination against the human papilloma virus (HPV) -- the causative virus that leads to inflammation and eventually cancer of the cervix -- has the potential to reduce those rates even further, but the vaccine is given only to young people with no prior exposure to the virus.

The possibility of IUDs as a risk reducer is an intriguing notion that's been raised before. Intrauterine devices (IUDs) -- used in the United States since the late 1950s -- prevent sperm from joining with the egg by either damaging the sperm or creating a hostile environment for it. A 2011 study analyzed cervical cancer rates among women from 11 countries who had used an IUD and among women who hadn't. Women who had a history of IUD use had half the risk of developing cervical cancer as women with no IUD use, regardless of whether the use was for 10 years or only one year. There was no difference in HPV infection rates between the two groups, so obviously some other factor was involved.

The recent study you mention was a review of 16 studies exploring the link between cervical cancer and IUDs. The studies were from the 1980s and 1990s, and three of them were performed in the United States. Overall, cervical cancer rates were 30 percent lower among women using the device compared to nonusers. Keep in mind that the finding was a correlation and so does not prove that IUDs actually lower the rate of cervical cancer. But the authors surmised that the reason IUDs could potentially reduce the risk of cervical cancer is because insertion of an IUD causes an inflammatory reaction that increases the immune response in the cervix. This could lead to the clearance of the human papilloma virus.

The results of another study, one that followed 676 sexually active women in San Francisco from 2000 to 2014, conflict with this theory. The average age of the women at the beginning of the study was about 18. The women were routinely tested for HPV, and 85 of them used an IUD at some point during the study. No benefit was seen in either the acquisition or the clearance of HPV in women using an IUD. The authors of this study wondered if IUDs decreased the incidence of cervical cancer by somehow clearing precancerous lesions in the cervix.

In conclusion, I'm not certain that getting an IUD for the purpose of decreasing cervical cancer risk is necessary. It seems even less necessary if you have had multiple negative HPV tests and Pap smears. Nonetheless, for women making an initial birth control choice who are weighing the risks and benefits of an IUD, these studies may be an influencing factor.

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Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.

Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.

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