Fig. 1From: Progesterone vs. synthetic progestins and the risk of breast cancer: a systematic review and meta-analysisStudy selection process. The initial search resulted in 3410 citations. After screening the abstracts, this was limited to 46 potentially relevant articles. These were reviewed in full text by two authors and eventually two cohort studies and one population-based case-control study were included with 44 being excludedBack to article page