How do oral contraceptives affect cervical cancer risk?

Evidence shows that long-term use of oral contraceptives (OCs) (5 or more years) may be associated with an increased risk of cancer of the cervix (the narrow, lower portion of the uterus). Although OC use may increase the risk of cervical cancer, human papillomavirus (HPV) is recognized as the major cause of this disease. Approximately 14 types of HPV have been identified as having the potential to cause cancer, and HPVs have been found in 99 percent of cervical cancer biopsy specimens worldwide.

A 2003 analysis by the International Agency for Research on Cancer (IARC) found an increased risk of cervical cancer with longer use of OCs. Researchers analyzed data from 28 studies that included 12,531 women with cervical cancer. The data suggested that the risk of cervical cancer may decrease after OC use stops. In another IARC report, data from eight studies were combined to assess the effect of OC use on cervical cancer risk in HPV-positive women. Researchers found a fourfold increase in risk among women who had used OCs for longer than 5 years. Risk was also increased among women who began using OCs before age 20 and women who had used OCs within the past 5 years. The IARC is planning a study to reanalyze all data related to OC use and cervical cancer risk.

This answer is based on source information from National Cancer Institute.