Cervical Cancer Risk Factors

Cervical cancer is unusual. Doctors know almost exactly what causes it: long-lasting infection with certain types of HPV, the human papillomavirus. That is also why it is one of the most preventable cancers. Vaccination and regular screening both help.

HPV is a very common virus. It spreads mainly through sexual contact. Most people who get it clear the infection on their own within one to two years. Many never know they had it. Trouble starts when a high-risk type lingers instead of clearing. Over years, a lasting infection can change cervical cells. Some of those changes eventually become cancer. Two HPV types, called 16 and 18, cause about 70% of cervical cancers worldwide.

Long-lasting infection with high-risk HPV causes almost all cervical cancer.

A weakened immune system makes it harder to clear HPV. That means infection is more likely to stick around. This includes people living with HIV. It includes people who have had an organ transplant. It also includes people taking medicines that suppress the immune system.

Smoking raises risk too. This is true whether you smoke directly or breathe secondhand smoke often. Chemicals from tobacco seem to weaken the immune system's fight against HPV in the cervix. More smoking is linked to more risk.

A few other things raise risk, though scientists do not fully know why. These include long-term use of birth control pills. They include having many full-term pregnancies. Obesity and starting sexual activity at a young age are on the list too. None of these causes cervical cancer alone. They seem to add risk mainly by affecting whether HPV persists or causes lasting change.

Skipping regular screening is its own risk factor. It does not raise your chance of getting HPV. It raises the chance that a change on the cervix goes unnoticed until it becomes cancer.

The HPV vaccine, brand name Gardasil 9, prevents infection with nine HPV types. Seven of them are high-risk types that cause most cervical cancers, and the other two cause most genital warts. It works best before someone becomes sexually active. That is why the CDC recommends routine vaccination at ages 11 to 12. Older teens and adults up to age 45 can benefit too. Talk with a doctor about timing.

The vaccine does not protect against every cancer-causing HPV type. That is why regular screening still matters, usually starting in your 20s. A Pap test looks for abnormal cervical cells. An HPV test looks for the virus itself. Together, they catch problems years before cancer could develop. Condoms lower the chance of spreading HPV during sex. They do not fully prevent it, since HPV can infect skin a condom does not cover.

Ask whether you are up to date on cervical screening. Ask how often you need it. Ask whether you or your children should get the HPV vaccine, and when. Ask whether anything in your health history raises your risk. Ask what an abnormal result would mean for next steps.

The CDC recommends starting Pap tests at age 21. From 21 to 29, a Pap test every three years is standard if results stay normal. From 30 to 65, you have three options: an HPV test alone every five years, an HPV and Pap test together every five years, or a Pap test alone every three years. After 65, some people can stop screening if their recent results have been normal and they have no history of precancerous changes. Ask your doctor which schedule fits you.

• National Cancer Institute — Cervical Cancer Causes, Risk Factors, and Prevention
• National Cancer Institute — Human Papillomavirus (HPV) Vaccines