Influence of oral contraceptives on the incidence of premalignant and malignant lesions of the cervix.

The effect of oral contraceptive use on the development of severe dysplasia, carcinoma in situ and invasive carcinoma of the cervix was studied by a prospective longitudinal survey of 32,000 women. They were enrolled into the study between the ages of 15 and 39. Some had started oral contraceptive use before enrollment, others started after enrollment and some remained non-users throughout the study period. They were followed-up to 6-1/2 years. Analyses were performed on data from 24,784 women who met our criteria for incidence. Data were adjusted for years of follow-up, age at enrollment, age at first pregnancy, number of pregnancies, number of smears, and duration of use.