This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: ThereThere is solid evidence breastfeeding lowers the risk of breast cancer. Findings from large pooled and meta-analyses that combined data from many studies show women who breastfeed have a lower risk of developing breast cancer compared to those who do not [1-3].
A meta-analysis of five case-control studies found breastfeeding reduced the risk of both hormone receptor-positive (estrogen receptor-positive and/or progesterone receptor-positive) and hormone receptor-negative (estrogen receptor-negative and/or progesterone receptor-negative) breast cancers .
Learn more about breastfeeding and breast cancer risk.
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Study selection criteria: Large pooled and meta-analyses.
Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Relative Risk of Breast Cancer in Women who Breastfed Compared to Women who Did NotRR (95% CI)
Pooled and meta-analyses
Nelson et al. 
Bernier et al. 
* For one year of breastfeeding
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