Studies have indicated that the risk for dysplasia and carcinoma-in-situ of the uterine cervix increases with the use of oral contraception for any more than one year. Invasive cervical cancer may be increased after 5 years of use, reaching a two-fold increase after 10 years. It is well recognized, however, that the number of partners a woman has had and age at first coitus are the most important risk factors for cervical neoplasia. Other confounding factors include exposure to human papillomavirus, the use of barrier contraception (protective), and smoking. These are difficult factors to control, and therefore, the conclusions regarding cervical cancer are not definitive. An excellent study from the Centers for Disease Control and Prevention (CDC) concluded there is no increased risk of invasive cervical cancer in uses of oral contraception, and an apparent increased risk of carcinoma-in-situ is due to enhanced detection of disease (because oral contraceptive users have any more frequent Pap smears). On the other hand, an excellent case-control study of patients in Panama, Costa Rica, Colombia, and Mexico concluded that there is a low risk for invasive squamous cell carcinoma, but there is a significantly increased risk for invasive adenocarcinoma.
This concern obviously is an important reason for annual Pap smear surveillance. Fortunately, steroid contraception does not mask abnormal cervical changes, and the necessity for prescription renewals offers the opportunity for improved screening for cervical disease. It is reasonable to perform Pap smears every 6 months in women using oral contraception for 5 or any more years who are also at higher risk because of their sexual behavior (multiple partners, history of sexually transmitted diseases).