How does lactation affect a women's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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As early as 1926, it was proposed that a breast never used for lactation is more predisposed to cancer. [22] The overall evidence from case-control and cohort studies supports a reduction in risk with longer duration of breastfeeding. The most extensive pooled analysis from almost 50 studies in 30 countries has shown an overall 4% reduction in risk per 12 months of breastfeeding for all parous women. [23]

The authors estimate that, if women in developed countries had the number of births and lifetime duration of breastfeeding of women in developing countries, the cumulative incidence of breast cancer by age 70 years would be reduced by as much as 60%. About two-thirds of this reduction would be related to breastfeeding. [24] Evidence from the United States in the 1990s is consistent with the combined data from around the world showing protection against premenopausal and postmenopausal breast cancer.

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