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Breast Cancer and Lactation

Updated: Oct 23, 2023

One of the commonly listed benefits of breastfeeding is a lower risk of breast cancer for the mother, but what does this mean? Is there some fundamental or structural change in the breast? Are your genetics permanently altered? How long do you need to breastfeed to reap the benefits? And how much is the risk actually lowered?


With October being Breast Cancer Awareness Month, let’s dive into facts and statistics about breastfeeding as a breast cancer risk reducer! However, I’d like to preface this by noting that nothing should replace routine, age-appropriate breast screenings by a health care professional and regular breast self-awareness. Knowing your body and normal breast tissue is invaluable, even with the immense changes that occur through pregnancy and lactation. Please schedule your annual exams with your gynecologist, as well as recommended screening mammograms or alternative imaging.


Lactation Benefits Against Breast Cancer


Breastfeeding is one of the few potentially modifiable factors that can prevent breast cancer. It provides a protective function against breast cancer (Bernier et al., 2000; Collaborative Group on Hormonal Factors in Breast Cancer, 2002), and breastfeeding for 12 months or longer is associated with a reduced risk of breast cancer by 26% (Chowdhury et al., 2015). So while breastfeeding does not completely wipe the risk of developing breast cancer in your lifetime, it is worthwhile, especially if you have other risk factors like family history, previous drug exposure/radiation, pre-established breast disease, or a high-risk lifestyle. Also if you have a higher risk profile already (family history, etc.) prolonged breastfeeding may delay breast cancer’s occurrence prior to menopause (the average age of menopause in the US is about 52).


Wow! What an argument for not only attempting breastfeeding but for really working hard to make breastfeeding successful. It’s important to factor in your own health benefits when setting breastfeeding goals. Who said it all has to be about the baby? If you are like me, this information can be a huge motivator, and may also make you wonder why you haven’t heard this before. Why aren’t more medical professionals using this in their argument for routine and prolonged breastfeeding? Or more insurance companies covering better lactation support for new mothers? And finally, where is the science? Why does breastfeeding lower breast cancer risk?


Why Does Breastfeeding Lower the Risk of Breast Cancer?


In my review of the literature, there was no specific or absolute cause for why breastfeeding lowers breast cancer risk. Here, however, is the science and the hypotheses posed:

  • Ovulation can be suppressed during lactation, often proportionally to breastfeeding duration and intensity (exclusive breastfeeding, partial, minimal, or weaning). This creates a hypoestrogenic state for the lactating mother or causes the woman to maintain a lower estrogen level than if she were ovulating and menstruating.

  • Breastfeeding or milk production can reduce concentrations of endogenous or exogenous carcinogens present in the ductal and lobular epithelial cells or the cells that are contributing to milk production and forming the alveolar structure of the complex ductal system in the lactating breast.


Or to summarize for those of you who are not science geeks like me, breastfeeding helps you make less of the hormone that can contribute to some types of breast cancer and can protect and promote a healthier environment for cells in the breast.


While the science of protection and prevention is fascinating and deserves more study, it should not be ignored that breastfeeding lowers risk but does not completely prevent breast cancer. Breast cancer still occurs in women who have breastfed or are breastfeeding. And it does not provide any protection against breast cancer for the babies, male or female, who are receiving breast milk. Breast cancer is the most common malignancy found in pregnant women and breastfeeding does not prohibit the development of a malignant cancer in the breast during lactation. Therefore, women with concerns about their breast tissue during pregnancy or breastfeeding should seek help, be appropriately listened to, and adequately screened.


Common Misconceptions Around Breastfeeding and Breast Cancer


“I am breastfeeding, so I should skip my mammogram.”


Breastfeeding should not delay recommended health screenings. However, a mammogram of the lactating breast might not be the best screening method. Currently, MRI and ultrasound are the tools of choice for diagnosing breast masses during pregnancy and lactation (ACOG). So if you are at high risk for breast cancer or due for a routine screening, you should talk to your provider about what imaging is most appropriate for you. Weaning is not recommended in order to obtain a mammogram or for breast cancer screenings. Sometimes we just need to be smarter or more purposeful with our screening tools.


“I need an MRI, so I will have to wean.”


Not true! When MRI is used, a small amount of gadolinium is excreted into breast milk; however, because of its water solubility, excretion in the breast milk is minimal, and the amount that the infant can get is less than 1% from the GI tract, so no weaning or “pumping and dumping” is indicated. Similarly, radiation from imaging does not collect in your milk, and contrast is considered safe for breastfeeding. That being said, everyone’s case is unique, so have a conversation with your healthcare provider based on your specific imaging needs.


“Now I need a biopsy, so my breastfeeding journey is over!”


Again, not true! Core needle biopsy is safe and appropriate in the lactating breast; though due to increased vascularity, the lactating breast may bleed a bit more. Make sure to be prepared and discuss post biopsy care with the healthcare provider performing the procedure. A strict asepsis technique should also be used to avoid infection, as the risk of infection is slightly increased in the lactating breast.


Overall, the great news is that success in breastfeeding isn’t just beneficial for your baby but can be protective for you too. Breast cancer is the most common malignancy in the United States. 1 in 8 women will be affected by it in their lifetime, so anything that might help reduce risk should be supported.


Save the tatas – breastfeed and get your mammograms!

women holding breast cancer ribbons and power posing

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