Barcellos-Hoff M

Introduction A woman’s risk to get breast cancer is affected by her reproductive history and hence exposure to reproductive hormones. An early full-term pregnancy has protective effects (MacMahon et al., 1970), whereas risk increases with the number of menstrual cycles she experiences during her life time, that is with shorter cycles, younger age at menarche, and later menopause (Colditz et al., 2004).