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Study: Breastfeeding Lowers Breast Cancer Risk in Women with Family History of the Disease (dateline January 23, 2010)

Breastfeeding may significantly reduce the chances of developing breast cancer among women with a family history of the disease, according to the results of a recent study. Researchers found that women with a family history of breast cancer who breastfed their children reduced their risk of developing breast cancer by more than half compared to those who did not breastfeed. The American Academy of Pediatricians and the National Association of Pediatric Nurses Associates and Practitioners already recommend breastfeeding as much as possible during the baby's first year to improve a baby's health and prevention infections and allergies. This new study suggests a potential additional benefit of reducing breast cancer risk for some women.

To conduct their study, lead researcher Alison Stuebe, MD, assistant professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill School of Medicine, and colleagues reviewed data from the Nurses' Health Study II, a long-term study of more than 100,000 women from 14 states. According the university, the study followed more than 60,000 who reported at least one pregnancy in 1997, when breastfeeding was assessed in detail, and followed them through 2005 to determine how many developed invasive breast cancer.

The results of the study, which were published in the Archives of Internal Medicine, found that women with a family history of breast cancer were 59 percent less likely to develop breast cancer if they breastfed their children.

"This is good news for women with a family history of breast cancer," said Dr. Stuebe, MD in a university news release. "Our results suggest a woman can lower her risk of cancer simply by breastfeeding her children."

While the researchers did not examine why breastfeeding may reduce breast cancer risk, the researchers suggested that inflammation and engorgement shortly after birth may cause changes in breast tissue that could increase risk for breast cancer. They said that breastfeeding followed by weaning may prevent this inflammation. According the researchers, the length of time a woman breastfed did not appear to influence breast cancer risk. In the study, women who breastfed three months reduce their breast cancer risk the same as women who breastfed three years.

However, the researchers did not find a reduction in breast cancer risk for women without a family history of the disease. "This could be because there's something about genetically caused breast cancer that's affected by breastfeeding, or it could be because rates of breast cancer were so low in women without a family history that we couldn't see an association in this data set," said Dr. Stuebe, in the news release.

Other studies have shown that breastfeeding may help protect against infant ear infections, allergies, diarrhea, eczema, bacterial meningitis, and other serious illnesses. Research has also shown that breastfeeding reduces infant anemia (iron deficiency in the blood) and stomach or intestinal infections. Breast-feeding also offers benefits to nursing mothers. Breastfeeding releases hormones which cause the uterus to shrink after delivery and also decreases bleeding. Mothers who breastfeed typically have an easier time losing weight after pregnancy. According to the American Academy of Pediatrics, breastfeeding also helps build a woman's bone mineral density and helps prevent osteoporosis after menopause.

Additional Resources and References

  • This article references the August 10, 2009, University of North Carolina at Chapel Hill School of Medicine new release, "Breastfeeding Reduces Risk of Breast Cancer in Some Women," which was published on the UNC Health Care web site at
  • The study, "Lactation and Incidence of Premenopausal Breast Cancer"' was published in the Vol, 169, Issue 15 (Aug 10/24, 2009) of the Archives of Internal Medicine,
  • To learn more about breastfeeding, please visit