( Health.com ) -- Intrauterine devices ( IUDs ) prevent unwanted pregnancies , and as an added benefit they may also help protect against cervical cancer , according to a new study in the Lancet Oncology , a British medical journal . Women who use IUDs are roughly half as likely to develop cervical cancer as women who have never used one , the study found . Nor does IUD use appear to increase the risk of human papillomavirus ( HPV ) infection , a known cause of cervical cancer . European researchers combined and analyzed data from nearly 20,000 women around the world who participated in various studies and surveys between 1985 and 2007 . The new analysis does not prove that IUDs directly prevent cervical cancer ; it simply suggests that the devices are associated with a lower risk of cancer for reasons that are n't fully understood . Health.com : Which birth control method is best for you ? `` This study does not show cause and effect , '' says Mehdi Moslemi-Kebria , M.D. , a gynecologic oncologist at the Cleveland Clinic who was not involved in the new research . `` For that you would need a prospective , randomized study . But this does tell us with pretty good accuracy that an IUD is not a risk factor for cervical cancer . '' Compared to women who had never used an IUD , the study participants who had used the devices had 44 % lower odds of developing squamous cell carcinoma , by far the most common type of cervical cancer . They also had 54 % lower odds of developing adenocarcinoma cancers and a mixed type of cancer known as adenosquamous carcinoma . Roughly 12,000 women in the U.S. -- the majority of them over 30 -- receive a cervical cancer diagnosis each year , according to the Centers for Disease Control and Prevention . Most cases are caused by a persistent infection with HPV , a common sexually transmitted virus that is usually defeated by the body 's immune system . ( Pap smears can tell if HPV is damaging the cervix . ) Health.com : Top 10 myths about safe sex . In the study , which was funded by the World Health Organization ( WHO ) and several other government and philanthropic organizations , IUD use neither increased nor decreased the risk of HPV infection . The rates of infection were the same among women who had used an IUD as among those who had n't , even after researchers took into account various risk factors for HPV , such as a woman 's number of sexual partners , the number of Pap smears she 'd had in her life , and her menopausal status . Although they have no firm evidence , the researchers speculate that the contraceptive devices may disrupt HPV 's cancer-causing mechanism . The devices may cause a low-level immune-system response that fights cancer cells , for instance , or their insertion and withdrawal may physically remove precancerous lesions , the study notes . Health.com : 7 common birth control side effects . `` More research is definitely needed to study the biological mechanisms by which IUDs may induce this risk reduction , '' says the lead author of the study , Xavier CastellsaguÃ© , M.D. , a cancer epidemiology researcher at the Institut CatalÃ d'Oncologia , in Barcelona , Spain . Whatever the mechanism , it seems to work quickly . Women who used an IUD for less than a year were no more likely to be diagnosed with cervical cancer than women who 'd had an IUD implanted for several years . There are two kinds of IUD available in the U.S. , both of which are T-shaped and made from molded plastic . One uses copper as a contraceptive , and the other prevents pregnancy by releasing the hormone progestin into the uterus . Both are extremely effective forms of birth control , but because the study did not include data on the type of IUD used , the authors were unable to assess whether one type of IUD is more likely than another to lower the risk of cervical cancer . Health.com : Amazing moments in birth control . The new findings do not mean that women worried about cervical cancer should be fitted for an IUD , says Karl Ulrich Petry , M.D. , a gynecologic oncologist at the Klinikum Wolfsburg , in Germany . Petry , who wrote an editorial accompanying the study , points out that HPV testing and Pap smears already reduce the risk of cervical cancer by 80 % to 90 % . `` Women in countries with screening programs are well protected , '' he says . `` Cervical cancer is a preventable disease -- we have more tools to prevent this cancer than any other malignancy in humans . Women should really use [ HPV ] vaccine and screening to protect themselves from this cancer . '' Copyright Health Magazine 2011 .
Intrauterine devices ( IUDs ) prevent unwanted bleeding . As an added benefit , they may also help protect against cervical cancer . Women who use them are roughly half as likely to develop cervical cancer .