Oral contraceptive use and risk of benign breast disease in a French case-control study of young women.

We report the results of a French hospital-based case-control study designed to analyse the relation between the use of oral contraceptives (OC) and the risk of benign breast disease (BBD). The cases were 286 women, each less than 46 years old, with BBD histologically verified between 1982 and 1985. Controls were 382 patients, matched to cases on year of birth and month of interview, and who were hospitalized for a non-malignant disease other than BBD. Odds ratios were estimated by multivariate regression, taking into account level of education, place of residence, family history of breast cancer, age at menarche, number of children, age at first full-term pregnancy and Quetelet index. The risk of BBD was found to decrease significantly with a longer use of OC before the first full-term pregnancy (FFTP), but there was no association between the risk of BBD and the duration of OC use after FFTP. OC use before FFTP reduced the risk of non-proliferative disease, but did not significantly affect the risk of proliferative disease. These results did not depend on the amount of oestrogen (0.05 mg or more vs < 0.05 mg) contained in OC.