Intrauterine devices (IUDs), the small plastic devices inserted into the uterus to prevent pregnancy, may also offer women protection against cervical cancer, according to a new study published in The Lancet.
An international team of researchers analyzed 26 studies that included nearly 20,000 women from 14 countries and found that the risk of cervical cancer in women who used IUDs was nearly half that of women who never used them.
While the researchers did not find a link between IUDs and a lower risk of infection with human papilloma virus (HPV), the virus that leads to cervical cancer, the study authors believe IUDs may cause an immune response that can get rid of the virus once it enters the body.
"The hypothesis is that an IUD, because it's a foreign body, creates an inflammatory response that gets rid of the HPV, which reduces the risk of cervical cancer," said Dr. Howard Jones, chair of obstetrics and gynecology at Vanderbilt University School of Medicine.
"People have suggested inthe past that having an IUD put people at increased risk for developing cancer, and we are not seeing that," said Dr. Ira Horowitz, professor and director of gynecological oncology at the Winship Cancer Institute of Emory University in Atlanta.
Previous studes have found IUD use reduces the risk of endometrial cancer, but few have looked at the relationship between IUDs and cervial cancer.
Experts not involved with the research say while the findings offer important insight into how cervical cancer develops, clinicians are unlikely to change how they prescribe IUDs as a result of this research since this study does not determine whether a cause-and-effect relationship exists between IUDs and cervical cancer. The study also did not evaluate specific types of IUDs.
"The protective effect of IUD use challenges some key elements in the current model of the natural history of cervical cancer," wrote Dr. Karl Ulrich Petry of Klinikum Wolfsburg in Wolfsburg, Germany, in an accompanying comment.
"These data may be reassuring for women who have IUDs, but I don't there will be a substantial impact on prescribing them," said Dr. Johnathan Lancaster, director of the Center for Women's Oncology at Moffitt Cancer Center in Tampa.
IUDs are expensive and can cause complications, such as pain and heavier bleeding during menstruation, so doctors don't believe the benefits outweigh the risks. Barrier methods, such as condoms, are a better option for women who are more sexually active.
"Condoms reduce the risk of both HPV infection and HIV infection," said Jones.
Doctors typically prescribe IUDs to women in monogamous relationships who have had at least one child and don't plan to have any more for quite some time.
Experts also say women using these devices should get regular Pap smears.
"This does not mean that women who have IUDs should change their practice of cervical screening," said Lancaster.
Currently, screening guidelines recommend that women who are sexually active should have a Pap smear every year. Starting at age 30, women who have had three normal Pap tests may opt for screening every two to three years.