Sept. 12, 2011 -- Women who use intrauterine devices (IUDs) for birth control, even for a short time, have a lower cervical cancer risk than those with no history of IUD use, new research suggests.
Compared to women who had never used an IUD, the international study found that those who had used the implanted contraceptive had almost half the risk for developing cervical cancer, which is caused by infection with the sexually transmitted human papilloma virus (HPV).
IUD use is known to reduce endometrial cancer risk. But the impact of the birth control method on cervical cancer and HPV infection has not been clear, says study researcher Xavier Castellsague, PhD, of Catalonia, Spain's Institut Castala d'Oncologia.
The study is published online The Lancet Oncology.
"The good news for IUD users is that this form of birth control does not increase the risk of HPV infection and it appears to lower the risk for developing cervical cancer," he tells WebMD.
Castellsague and colleagues analyzed data from 10 previously published studies that compared women with cervical cancer to women without the disease and 16 HPV frequency surveys conducted in 14 countries.
The researchers concluded that IUD use did not affect HPV infection risk. But IUD use reduces the risk for developing both major types of cervical cancer: squamous cell and adenosquamous carcinoma.
The risk for both cancers was found to be reduced by nearly half during the first year of IUD use. A similar level of protection was seen in women who had used the implanted birth control device for as long as a decade.
The researchers have several theories that may explain how the implanted contraceptive protects against cervical cancer.
IUDs are small, T-shaped plastic devices placed in the uterus by a health care professional to prevent fertilization and implantation of the egg. One type of IUD is wrapped in copper while another type contains a form of the hormone progestin.
One theory is that the procedure to insert or remove an IUD may destroy HPV-related lesions before they become cancerous. Another is that hormone-targeting IUDs affect the natural history of HPV infection.