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For many babies, breast milk is the best source of nutrition. It also provides numerous health benefits, including protection against many common childhood infections, such as colds and respiratory illnesses. Breastfed infants are also less likely to develop asthma, allergies, ear infections, type 2 diabetes and obesity. And the skin-to-skin contact that occurs during breastfeeding may have both physical and emotional benefits for both mother and child.

Many people are aware of these positive effects of breastfeeding. However, a lesser-known benefit is a potential reduction in a woman’s cancer risk.

Does breastfeeding reduce the risk of breast cancer?

Recently, a large scientific study showed a 4.3% decline in breast cancer risk for every 12 months a woman breastfeeds. A second study showed that breastfeeding women were 14% less likely to develop breast cancer in their lifetime than their non-breastfeeding counterparts.

Researchers believe this phenomenon may be related to hormonal changes that can delay menstruation, which often occur in a woman’s body while she is breastfeeding. For instance, if a woman breastfeeds exclusively and on demand (e.g., in the middle of the night), she may not have a menstrual period for up to several months until her baby is weaned. In general, the more menstrual cycles a woman has over her lifetime, the higher her exposure to the hormones estrogen and progesterone, both of which have been conclusively linked to an increased risk of breast and ovarian cancers.

Another possible explanation is that when breast cells are busy producing milk 24/7, they may have fewer opportunities to “misbehave.” Breast cancer develops when breast cells mutate, usually for an unknown reason. As a result of the mutation, the cells begin to grow and divide very rapidly, then the excess cells bind together and form tumors.

Finally, many women adopt healthy lifestyle practices while breastfeeding, such as eating nutritious foods and not drinking alcoholic beverages or smoking. These positive steps can help lower a women’s cancer risk.


Can a woman develop breast cancer while she is breastfeeding?

Breast cancer can develop at any time during a woman’s life, and it is no more or less likely to occur while she is nursing. However, a woman may be more attuned to changes in her breasts during that time, and therefore more likely to notice potential warning signs of cancer, such as a breast lump or pain. Due to the effects of milk production and/or blocked milk ducts, a nursing mother’s breasts may feel lumpy. In general, any breast lump that does not get smaller or go away within a week should be checked by a physician.

If you would like to review your personal breast cancer risk profile with a specialist, you can request an appointment with an oncologist in the Don & Erika Wallace Comprehensive Breast Program at Moffitt Cancer Center. Call 1-888-663-3488 or complete a new patient registration form online to connect with a cancer expert as soon as possible. As our patient, you are a priority of Florida’s top cancer hospital, which is changing the model and delivering nationally ranked care in new and transformative ways.