Cervical cancer is caused by severe abnormal changes in the cells of the cervix. Most precancerous or cancerous cell changes occur in the cervix at the transformation zone because these cells normally undergo constant change. During this natural process of change, some cervical cells can become abnormal if you are infected with high-risk types of HPV.

Other factors that may play a role in causing cervical cancer include:

• Having sex before age 16.¹
• Having more than one sex partner, or having a sex partner who has more than one partner.²
• Smoking or a history of smoking. Smoking seems to make HPV infections last longer.³ One study shows that your risk of cervical cell changes may also increase if you are around someone else while they smoke (secondhand smoke).⁴ Cervical cell changes are more likely to go away on their own in women who don't smoke.
• Having an impaired immune system, such as from having human immunodeficiency virus (HIV).
• Using birth control pills for more than 5 years. This may be related to infection with HPV.⁵

Regular Pap test screening is the single most important tool to identify cervical cell changes early before they progress to cancer.