Most cervical cancers start with HPV, but other factors can raise your risk

Human papillomavirus (HPV) causes about 90 percent of cervical cancers, but it is not the only pathway to the disease. Smoking, a weakened immune system, long-term use of oral contraceptives, and a history of sexually transmitted infections can all increase risk independently or work alongside HPV infection. Some women develop cervical cancer without ever testing positive for HPV, which means understanding these other contributors matters for your own risk picture.

The cervix is vulnerable to cancer through multiple routes because its cells are constantly exposed to the environment and to substances that pass through the reproductive tract. When you know what raises your risk beyond HPV, you can make more informed choices about screening frequency, lifestyle changes, and conversations with your doctor.

Key Takeaways

  • Smoking damages the immune cells in the cervix and makes it harder for your body to clear HPV infections, even if you carry the virus.
  • A weakened immune system from HIV, immunosuppressive medications, or organ transplant can allow precancerous changes to develop faster and progress to cancer.
  • Long-term oral contraceptive use (five years or longer) slightly raises cervical cancer risk, though the benefit of preventing pregnancy often outweighs this small increase.
  • A history of other sexually transmitted infections like chlamydia may increase risk, though HPV remains the dominant cause.
  • Screening with Pap tests or HPV tests catches precancerous changes before they become cancer, regardless of which risk factors you have.

How smoking changes the cervix and immune response

Smoking introduces carcinogens directly into the bloodstream and cervical tissue. These chemicals accumulate in cervical mucus and can damage the DNA of cervical cells. More importantly, smoking weakens the local immune response in the cervix—the white blood cells that normally patrol and clear away abnormal cells work less effectively in smokers.

This matters most for women who also carry HPV. A woman with HPV who smokes is significantly more likely to develop precancerous changes (cervical dysplasia) than a woman with HPV who does not smoke. The combination of a persistent virus and a compromised local immune system creates conditions where abnormal cells can multiply unchecked. Quitting smoking at any age improves immune function and lowers this risk.

Immune system weakness and cervical cancer risk

Any condition that weakens your immune system raises the risk that HPV infection will persist and progress to cancer. Women with HIV who have a low CD4 count (a measure of immune strength) develop cervical precancers and cancers at much higher rates than women without HIV. The same pattern appears in people who take immunosuppressive medications after an organ transplant or for autoimmune diseases.

The mechanism is straightforward: your immune system normally clears most HPV infections within one to two years. When immunity is weak, the virus lingers, and the longer it stays, the greater the chance that random mutations in cervical cells will accumulate and lead to cancer. Women with HIV or other immune conditions should discuss screening frequency with their doctor, as standard intervals may not be appropriate for them.

Oral contraceptive use and cervical cancer risk

Research shows that women who use oral contraceptives for five years or longer have a modestly higher risk of cervical cancer than women who have never used them. The risk appears to decline after stopping the pills. The reason is not fully understood—it may involve hormonal effects on cervical cells, changes in the vaginal environment that favor certain infections, or simply that long-term users have more sexual partners and thus more HPV exposure.

The absolute increase in risk is small, and for most women the benefit of preventing unwanted pregnancy outweighs this small increase. If you use oral contraceptives long-term, regular screening (Pap test or HPV test) is the most important step you can take. Discuss your personal risk factors with your doctor if you are considering switching contraceptive methods.

Other sexually transmitted infections and cervical health

Women with a history of chlamydia or other sexually transmitted infections show higher cervical cancer rates in some studies, though the link is weaker than with HPV. Chlamydia can cause chronic inflammation in the cervix, and inflammation itself may create an environment where precancerous changes are more likely to develop. Additionally, women who have had one sexually transmitted infection are more likely to have been exposed to HPV as well.

It is difficult to separate the effect of chlamydia itself from the effect of HPV co-infection, since both are sexually transmitted. What matters clinically is that if you have had a sexually transmitted infection, you have reason to ensure you are up to date on cervical cancer screening and to discuss your history with your healthcare provider.

Diethylstilbestrol (DES) exposure in the womb

Women whose mothers took the drug diethylstilbestrol (DES) during pregnancy—a practice that ended in the 1970s—have a higher risk of a rare type of vaginal and cervical cancer called clear cell adenocarcinoma. DES was a synthetic estrogen given to prevent miscarriage, and it altered the development of reproductive tissues in exposed fetuses. Most women exposed to DES in the womb are now in their 50s and older.

If your mother took DES while pregnant with you, your doctor should know this history. You may benefit from more frequent screening or different screening methods. The risk of DES-related cancer is real but still relatively uncommon, and screening can catch precancerous changes early.

Age, screening gaps, and undetected precancers

Cervical cancer develops over years, usually from precancerous changes that progress slowly. Women who have not had regular Pap tests or HPV tests are at much higher risk simply because precancers go undetected and untreated. A woman in her 40s or 50s who has never been screened is far more likely to present with invasive cancer than a woman who has been screened regularly.

Age itself is a risk factor in the sense that the longer cervical cells are exposed to carcinogens and the longer an HPV infection persists, the more time there is for the mutations that lead to cancer to accumulate. This is why screening guidelines typically begin at age 21 and continue through age 65 (or longer, depending on screening history). If you have had gaps in screening, discuss with your doctor whether you need catch-up testing.

Frequently Asked Questions

Can you get cervical cancer without HPV?

Yes, though it is uncommon. About 5 to 10 percent of cervical cancers occur in women who test negative for HPV. These cancers are more likely to be adenocarcinomas (arising from glandular cells rather than the flat cells that line the cervix) and may be linked to smoking, immune weakness, or other factors. Regular screening catches precancers before they become invasive, regardless of HPV status.

Does birth control cause cervical cancer?

Oral contraceptives slightly raise cervical cancer risk when used for five or more years, but the absolute increase is small. The benefit of preventing pregnancy usually outweighs this small risk. Other forms of birth control (condoms, IUDs, implants) do not carry the same association. If you are concerned, discuss your options with your doctor.

If I quit smoking, does my cervical cancer risk go down?

Yes. Quitting smoking improves immune function in the cervix and reduces the risk that HPV infection will persist and progress to cancer. The benefit appears within a few years of quitting. If you have HPV and smoke, quitting is one of the most important steps you can take to lower your cancer risk.

How often should I be screened if I have HIV?

Screening recommendations for women with HIV differ from standard guidelines and depend on your CD4 count and whether you have a history of abnormal Pap tests. Discuss screening frequency with your HIV care provider or gynecologist, as you may need testing more often than women without HIV.

What if I have had a gap in cervical cancer screening?

Tell your doctor how long it has been since your last screening. Depending on your age and screening history, you may need catch-up testing. A single Pap test or HPV test can often reassure you, though your doctor may recommend a different approach based on your individual situation.