Oral contraceptives and benign breast disease: a case-control study.Am J Obstet Gynecol 1984; 149(6):602-6AJ
The relationship between benign breast disease and use of oral contraceptives was analyzed in a case-control study conducted in Milan with 288 cases of clinically relevant and histologically confirmed benign breast disease and 285 age-matched controls with a spectrum of acute conditions apparently unrelated to use of oral contraceptives. Compared to the risk for women who had never used oral contraceptives, the relative risk for users was 1.0 (95% confidence interval: 0.6 to 1.5). There was no significant association with duration of use; however, a significantly lower relative risk was found in women using oral contraceptives during the year before breast biopsy (relative risk: 0.4; 95% confidence interval: 0.2 to 0.8). The protection in current users increased with increasing duration of use. In spite of this finding, the overall results of the present study do not support the hypothesis that oral contraceptive use protects against development of histologically confirmed and clinically relevant benign breast disease.