Oral contraceptives and cervical carcinoma in situ in Chile.

A case-control study of cervical carcinoma in situ was conducted in Santiago, Chile, to determine whether risk of this condition is altered by use of oral contraceptives. Responses to a standardized questionnaire were compared in 133 hospitalized cases and 254 age-matched controls selected from the same screening program through which the cases were detected. After controlling for the possible confounding influence of a variety of indices of sexual behavior, socioeconomic status, and prior cytological smears, no increase in risk was found in women who ever used oral contraceptives. No trend of increasing or decreasing risk was seen in relation to duration of use, up to more than 6 years of exposure, or with the passage of time from either initial or most recent exposure. An observed increase in risk in current users of oral contraceptives was not considered likely to represent a causal relationship.