- What is cervical cancer?
- What are the risk factors for cervical cancer?
- Signs and symptoms of cervical cancer
- Can cervical cancer be prevented?
- Finding cervical pre-cancers
- Other tests for women with abnormal cervical cytology results
- Work-up of abnormal Pap test results
- How women with abnormal Pap test results are treated to prevent cervical cancers from developing
- Cervical cancer prevention and screening: Financial issues
- Additional resources
What are the risk factors for cervical cancer?
A risk factor is anything that changes your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for many cancers. But having a risk factor, or even several, does not mean that you will get the disease.
Several risk factors increase your chance of getting cervical cancer. Women without any of these risk factors rarely develop cervical cancer. Although these factors increase the odds of getting cervical cancer, many women with these risk factors do not develop this disease. When a woman develops cervical cancer or pre-cancerous changes of the cervix, it is not possible to say with certainty that a particular risk factor was the cause.
In thinking about the following risk factors, it helps to focus on those you can change or avoid (like smoking or human papilloma virus infection), rather than those that you cannot (such as your age and family history). It is still important, though, to know about risk factors that cannot be changed, because it's even more important for women who have these factors to get regular Pap tests to detect cervical cancer early. Cervical cancer risk factors include:
Human papilloma virus infection
The most important risk factor for cervical cancer is infection by the human papilloma virus (HPV). HPV is a group of more than 100 related viruses, some of which cause a type of growth called a papilloma, or more commonly known as warts.
HPV can infect cells on the surface of the skin, and those lining the genitals, anus, mouth and throat, but not the blood or internal organs such as the heart or lungs.
HPV can be passed from one person to another during skin-to-skin contact. One way HPV is spread is through sex, including vaginal and anal intercourse and even oral sex.
Different types of HPV cause warts on different parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.
Certain types of HPV may cause warts to appear on or around the genital organs and in the anal area. These warts may barely be visible or they may be several inches across. These are known as genital warts or condyloma acuminatum. HPV 6 and HPV 11 are the 2 types of HPV that cause most cases of genital warts. They are called low-risk types of HPV because they are seldom linked to cervical cancer.
Other types of HPV are called high-risk types because they are strongly linked to cancers, including cancers of the cervix, vulva, and vagina in women, penile cancer in men, and anal and oral cancer in men and women. The high-risk types include HPV 16, HPV 18, HPV 31, HPV 33, and HPV 45, as well as some others. There might be no visible signs of infection with a high-risk HPV until pre-cancerous changes or cancer develops.
Doctors believe that a woman must be infected by HPV before she develops cervical cancer. Although this can mean infection with any of the high-risk types, about two-thirds of all cervical cancers are caused by HPV 16 and 18.
Infection with HPV is common, and in most people the body is able to clear the infection on its own. Sometimes, however, the infection does not go away and becomes chronic. Chronic infection, especially when it is with high-risk HPV types, can eventually cause certain cancers, such as cervical cancer.
Although HPV can be spread during sex − including vaginal intercourse, anal intercourse, and oral sex − sex doesn't have to occur for the infection to spread. All that is needed to pass HPV from one person to another is skin-to-skin contact with an area of the body infected with HPV. Infection with HPV seems to be able to be spread from one part of the body to another − for example, infection may start in the cervix and then spread to the vagina.
Completely avoiding putting the areas of your body that can become infected with HPV (like the mouth, anus, and genitals) in contact with those of another person may be the only way to truly prevent these areas from becoming infected with HPV.
The Pap test looks for changes in cervical cells caused by HPV infection. Other tests look for the infections themselves by finding genes (DNA) from HPV in the cells. For some women, the HPV test is used along with the Pap test as a part of screening. The HPV test may also be used to help decide what to do when a woman has a mildly abnormal Pap test result. If the test finds a high-risk type of HPV, it could mean she will need a full evaluation with a colposcopy procedure. Although there is currently no cure for HPV infection, there are ways to treat the warts and abnormal cell growth that HPV causes.
For more information on preventing HPV infection, see the "Things to do to prevent pre-cancers" section in this document or ask for our document Human Papilloma Virus (HPV), Cancer, and HPV Vaccines: Frequently Asked Questions.
Although scientists believe that it is necessary to have had HPV for cervical cancer to develop, most women with this virus do not develop cancer. Doctors believe that other factors must come into play for cancer to develop. Some of these known factors are listed below.
Women who smoke are about twice as likely as non-smokers to get cervical cancer. Smoking exposes the body to many cancer-causing chemicals that affect organs other than the lungs. These harmful substances are absorbed through the lungs and carried in the bloodstream throughout the body. Tobacco by-products have been found in the cervical mucus of women who smoke. Researchers believe that these substances damage the DNA of cervix cells, and may contribute to the development of cervical cancer. Smoking also makes the immune system less effective in fighting HPV infections.
Human immunodeficiency virus (HIV), the virus that causes AIDS, damages the immune system and puts women at higher risk for HPV infection. This might, in part, explain the increased risk of cervical cancer in women with AIDS. Also, that the immune system may be important in destroying cancer cells and slowing their growth and spread. In women with an impaired immune system from HIV, a cervical pre-cancer might develop into an invasive cancer faster than it normally would. Another group of women at risk of cervical cancer are women taking drugs to suppress their immune response, such as those being treated for an autoimmune disease (in which the immune system sees the body's own tissues as foreign and attacks them, as it would a germ) or those who have had an organ transplant.
Chlamydia is a relatively common kind of bacteria that can infect the reproductive system. It is spread by sexual contact. Chlamydia infection can cause pelvic inflammation, leading to infertility. Some studies have seen a higher risk of cervical cancer in women whose blood test results show signs of past or current chlamydia infection (compared with women with normal test results). Women who are infected with chlamydia often have no symptoms. In fact, they may not know that they are infected at all unless they are tested for chlamydia during a pelvic exam.
Women whose diets don’t include enough fruits and vegetables may be at increased risk for cervical cancer. Also, overweight women are more likely to develop adenocarcinoma of the cervix.
Oral contraceptives (birth control pills)
There is evidence that taking oral contraceptives (OCs) for a long time increases the risk of cancer of the cervix. Research suggests that the risk of cervical cancer goes up the longer a woman takes OCs, but the risk goes back down again after the OCs are stopped. In one study, the risk of cervical cancer was doubled in women who took birth control pills longer than 5 years, but the risk returned to normal 10 years after they were stopped.
The American Cancer Society believes that a woman and her doctor should discuss whether the benefits of using OCs outweigh this very slight potential risk. A woman with multiple sexual partners should use condoms to lower her risk of sexually transmitted infections no matter what other form of contraception she uses.
Intrauterine device use
A recent study found that women who had ever used an intrauterine device (IUD) had a lower risk of cervical cancer. The effect on risk was seen even in women who had an IUD for less than a year, and the protective effect remained after the IUDs were removed.
Using an IUD might also lower the risk of endometrial (uterine) cancer. However, IUDs do have some risks. A woman interested in using an IUD should first discuss the potential risks and benefits with her doctor. Also, a woman with multiple sexual partners should use condoms to lower her risk of sexually transmitted illnesses no matter what other form of contraception she uses.
Multiple full-term pregnancies
Women who have had 3 or more full-term pregnancies have an increased risk of developing cervical cancer. No one really knows why this is true. One theory is that these women had to have had unprotected intercourse to get pregnant, so they may have had more exposure to HPV. Also, studies have pointed to hormonal changes during pregnancy as possibly making women more susceptible to HPV infection or cancer growth. Another thought is that pregnant women might have weaker immune systems, allowing for HPV infection and cancer growth.
Young age at the first full-term pregnancy
Women who were younger than 17 years when they had their first full-term pregnancy are almost 2 times more likely to get cervical cancer later in life than women who waited to get pregnant until they were 25 years or older.
Poverty is also a risk factor for cervical cancer. Many women with low incomes do not have ready access to adequate health care services, including Pap tests. This means they might not get screened or treated for cervical cancers and pre-cancers.
DES is a hormonal drug that was given to some women to prevent miscarriage between 1940 and 1971. Women whose mothers took DES when pregnant with them are often called DES daughters. These women develop clear cell adenocarcinoma of the vagina or cervix more often than would normally be expected. This type of cancer is extremely rare in women who are not DES daughters. There is about 1 case of this type of cancer in every 1,000 women whose mother took DES during their pregnancy. This means that about 99.9% of DES daughters do not develop these cancers.
DES-related clear cell adenocarcinoma is more common in the vagina than the cervix. The risk appears to be greatest in women whose mothers took the drug during their first 16 weeks of pregnancy. The average age of women when they are diagnosed with DES-related clear-cell adenocarcinoma is 19 years. Since the use of DES during pregnancy was stopped by the FDA in 1971, even the youngest DES daughters are older than 35 − past the age of highest risk. Still, there is no age cut-off when these women are safe from DES-related cancer. Doctors do not know exactly how long women will remain at risk.
DES daughters may also be at increased risk of developing squamous cell cancers and pre-cancers of the cervix linked to HPV.
Although DES daughters have an increased risk of developing clear cell carcinomas, women don’t have to be exposed to DES for clear cell carcinoma to develop. It is extremely rare, but women were diagnosed with the disease before DES was invented.
You can learn more about DES in our separate document called DES Exposure: Questions and Answers. It can be read on our Web site, or call to have a free copy sent to you.
Family history of cervical cancer
Cervical cancer may run in some families. If a woman’s mother or sister had cervical cancer, her chances of developing the disease are 2 to 3 times higher than if no one in the family had it. Some researchers suspect some instances of this familial tendency are caused by an inherited condition that makes some women less able to fight off HPV infection than others. In other instances, women from the same family as a patient already diagnosed could be more likely to have one or more of the other non-genetic risk factors previously described in this section.
Last Medical Review: 05/02/2013
Last Revised: 05/02/2013