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Breast cancer and breastfeeding

This information came from a tag on Twitter at the weekend from a mum newly diagnosed with cancer weaning her baby from the breast prior to starting chemo. Hard enough I know but after the surgery she had been prescribed domperidone to control nausea – it stimulates milk production and no one seemed to know or have thought about this. She was prescribed ondansetron instead but only after providing her team with the information about domperidone.

I havent included lots of facts about the drugs as the data can change with research but it contains some of the things I have heard from mothers over the years and some sources of support.

If you need more information please contact me. I will do all I can to support your journey as cancer has raised its ugly head too often in my own family.


Breastfeeding can significantly reduce the risk of triple negative breast cancer (TNBC, the most aggressive breast cancers), probably in pre-menopausal women.

Breastfeeding may not affect the incidence or risk of hormone receptor positive disease (oestrogen and/or progesterone receptors) or HER2 disease.


Breastfeeding can lower breast cancer risk, especially if a woman breastfeeds for longer than 1 yearhttps://www.breastcancer.org/risk/factors/breastfeed_hist

Evidence on cancer and other diseases shows that sustained, exclusive breastfeeding is protective for the mother as well as the child https://www.wcrf.org/dietandcancer/recommendations/breastfeed-your-baby

Breastfeeding lowers the risk of developing breast cancer, particularly if you have your children when you are younger. The longer you breastfeed, the more the risk is reduced. It is not completely clear why this is. But the reduced risk might be because the ovaries don’t produce eggs so often during breastfeeding. Or it might be because breastfeeding changes the cells in the breast so they might be more resistant to changes that lead to cancer. https://www.cancerresearchuk.org/about-cancer/breast-cancer/risks-causes/protective-factors

So why have you been diagnosed with breast cancer?

A small number of women (approximately 100-120 each year in the UK) who breastfeed will still develop aggressive breast cancers (https://gpifn.org.uk/breast-cancer-risk-reduction/).  There are no certainties in life unfortunately and definitely no absolute protection against cancer because you are breastfeeding. Each year I hear from women who have been given the diagnosis that we all fear and are being forced to wean their babies in order to have treatment. So, a double loss is often described – the loss of life as it had been and the feelings around breastfeeding which is about so much more than milk.

Over the years I have “spoken” with many mothers who are looking for information on how long it takes for the chemotherapy drugs to leave their systems so that they can return to breastfeeding. That data is available particularly from the online database I can access Medications and Mothers Milk by Dr T H Hale, as well as LactMed.

Some mothers are determined to maintain their supply by pumping and dumping throughout treatment. That is a hard thing to do especially when dealing with the side effects of the drugs but I would do all in my power to support that choice. It is possible to relactate at the end of treatment when the drugs have left the body. The possible difficulty is that the baby may be reluctant to resume breastfeeding particularly if older as they can lose their suck. But who knows? Every mother and baby pair are individuals.

The decisions should always be those of the mother with as much information as can possible be ascertained from evidence-based sites and research.

Sources of support

You may feel lonely in the face of the diagnosis. Everyone will be focussing on your treatment and you may find that the advice to stop breastfeeding is almost a throw away comment. As mothers we know that stopping may not be as simple as it sounds. Our babies are reliant on breastfeeding not just for nutrition but also for comfort, for relief when they feel unwell, just because it feels good. To take that away suddenly is hard. It may be that your treatment will not take place for a little while and you can wean your baby from the breast slowly. However, for some it may need to be sudden and rapid. I have heard from mothers who want to continue to feed as normal until the very last moment, others who want to feel well enough to comfort their child during the period. Everyone has their own approach. There are medications to dry up the milk but they can have nasty side effects for some people although not all. Cabergoline is the best option. If weaning slowly the herb sage may be useful https://breastfeeding-and-medication.co.uk/fact-sheet/breastfeeding-and-lowering-stopping-milk-supply. Support from an experienced breastfeeding person can be invaluable so that you avoid symptoms of engorgement or mastitis. In the team supporting you there may be someone able to provide information, Lactation Consultants may be able to help or any of the voluntary breastfeeding charities will be knowledgeable in support.

Mummy’s Star supports women and their families with a diagnosis of during pregnancy or the postnatal period. https://www.mummysstar.org/  or on Facebook https://www.facebook.com/MummysStar

Depending on the age of your baby when you are diagnosed the Hearts Milk Bank may be able to provide donor breastmilk for a period (depending on availability) https://heartsmilkbank.org/ or on Facebook https://www.facebook.com/heartsmilkbank

Treatment Options

Your treatment plan will be individual to you but may involve surgery, chemotherapy, radiotherapy or a mixture of these.

As part of all of these interventions you may feel nauseous. Two of the drugs frequently prescribed are anti-emetic drugs which stimulate milk supply! These are domperidone and metoclopramide (this can also precipitate depression). Make sure that your team are aware of the potential difficulties of taking these drugs when you are trying to reduce your supply or dump what you are producing. There are alternatives such as ondansetron. Many anaesthetists, oncologists and GPs seem unaware of the potential to increase prolactin as they focus on treating you.

There are many chemotherapy agents and I do not intend to try to provide information on all of them in this sheet. If you want to email me wendy@breastfeeding-and-medication.co.uk I will be happy to discuss your regime with you and supply full information to your oncology team.

Email me wendy@breastfeeding-and-medication.co.uk or message me through the Facebook Page Breastfeeding and Medication

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