Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis. Mayo Clinic Proceedings 2006;81(10):1290–302

OBJECTIVE: To perform a meta-analysis of case-control studies that addressed whether prior oral contraceptive (OC) use is asso-ciated with premenopausal breast cancer. METHODS: We searched the MEDLINE and PubMed databases and bibliography reviews to identify case-control studies of OCs and premenopausal breast cancer published in or after 1980. Search terms used included breast neoplasms, oral contraceptives, con-traceptive agents, and case-control studies. Studies reported in all languages were included. Thirty-four studies were identified that met inclusion criteria. Two reviewers extracted data from original research articles or additional data provided by study authors. We used the DerSimonian-Laird method to compute pooled odds ratios (ORs) and confidence intervals (CIs) and the Mantel-Haenszel test to assess association between OC use and cancer