Figure 1. Flow diagram for study selection.

Studies from 1966-Jan. 2006 that addressed an association between breastfeeding history and breast cancer were obtained from a systematic review of breast cancer that addressed various risk factors. To obtain studies from Feb. 2006-present, we developed a search strategy that was based on that which was employed by the existing review. All studies from 1966-present were assessed for inclusion in this systematic review. Dashed lines surround the work that was previously published by Berrino, et al.