This information is from the National Cancer Institute (NCI).

By studying large numbers of women all over the world, researchers have identified certain risk factors that increase the chance that cells in the cervix will become abnormal or cancerous. They believe that, in many cases, cervical cancer develops when two or more risk factors act together.

Research has shown that women who began having sexual intercourse before age 18 and women who have had many sexual partners have an increased risk of developing cervical cancer. Women also are at increased risk if their partners began having sexual intercourse at a young age, have had many sexual partners, or were previously married to women who had cervical cancer.

Scientists do not know exactly why the sexual practices of women and their partners affect the risk of developing cervical cancer. However, research suggests that some sexually transmitted viruses can cause cells in the cervix to begin the series of changes that can lead to cancer. Women who have had many sexual partners or whose partners have had many sexual partners may have an increased risk for cervical cancer at least in part because they are more likely to get a sexually transmitted virus.

Scientists are studying the effects of sexually transmitted human papillomaviruses (HPVs). Some sexually transmitted HPVs cause genital warts (condylomata acuminata). In addition, scientists believe that some of these viruses may cause the growth of abnormal cells in the cervix and may play a role in cancer development. They have found that women who have HPV or whose partners have HPV have a higher-than-average risk of developing cervical cancer. However, most women who are infected with HPV do not develop cervical cancer, and the virus is not present in all women who have this disease. For these reasons, scientists believe that other factors act together with HPVs. For example, the genital herpesvirus also may play a role. Further research is needed to learn the exact role of these viruses and how they act together with other factors in the development of cervical cancer.

Smoking also increases the risk of cancer of the cervix, although it is not clear exactly how or why. The risk appears to increase with the number of cigarettes a woman smokes each day and with the number of years she has smoked.

Women whose mothers were given the drug diethylstilbestrol (DES) during pregnancy to prevent miscarriage also are at increased risk. (This drug was used for this purpose from about 1940 to 1970.) A rare type of vaginal and cervical cancer has been found in a small number of women whose mothers used DES.

Several reports suggest that women whose immune system is weakened are more likely than others to develop cervical cancer. For example, women who have the human immunodeficiency virus (HIV), which causes AIDS, are at increased risk. Also, organ transplant patients, who receive drugs that suppress the immune system to prevent rejection of the new organ, are more likely than others to develop precancerous lesions.

Some researchers believe that there is an increased risk of cervical cancer in women who use oral contraceptives (the pill). However, scientists have not found that the pill directly causes cancer of the cervix. This relationship is hard to prove because the two main risk factors for cervical cancer - intercourse at an early age and multiple sex partners - may be more common among women who use the pill than among those who do not. Still, oral contraceptive labels warn of this possible risk and advise women who use them to have yearly Pap tests.

Some research has shown that vitamin A may play a role in stopping or preventing cancerous changes in cells like those on the surface of the cervix. Further research with forms of vitamin A may help scientists learn more about preventing cancer of the cervix.

At present, early detection and treatment of precancerous tissue remain the most effective ways of preventing cervical cancer. Women should talk with their doctor about an appropriate schedule of checkups. The doctor's advice will be based on such factors as the women's age, medical history, and risk factors.

Source: “What You Need To Know About Cancer of the Cervix,” Brochure, NIH Publication Number 95-2047, National Cancer Institute, July 1994.

MSI-NCI089