My family has a history of breast cancer. Will breastfeeding increase my risk?
Breastfeeding lowers your chances of getting breast cancer. While you are producing breastmilk, your body makes less estrogen. Estrogen contributes to breast cancer. The longer you breastfeed, the lower your chances of getting breast cancer in the future.
SOURCE: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2888088/