Management of the spectrum of breast inflammation in lactation. Principle #1: frequent flexible breastfeeds or milk removal activate the stromal pump to relieve breast inflammation

Why frequent flexible milk removal is the fundamental principle of management of lactation-related breast inflammation

The most fundamental step in either prevention of, or the clinical management of, breast inflammation in lactation across the spectrum of presentations is to help the woman's breast experience repetitive contraction and dilation of the lactiferous ducts. This occurs with milk removal

• Usually by the infant directly breastfeeding, but

• May also be by mechanical milk removal if the woman has been pumping and feeding her baby expressed breast milk, prior to the episode of breast inflammation, or

• Hand expression of milk on occasions in addition to direct breastfeeding, because this also results in contraction of alveoli and dilation of lactiferous ducts. Hand expression shouldn't be necessary though if the baby is happy to take the affected breast frequently and flexibly.

Frequent flexible milk removal, directly from the breast by the infant, offering the affected breast first, will not result in a production mismatch. This is because we can trust infants to self-regulate at the breast, and refuse the breast when they don't want it.

Frequent flexible milk removal activates the stromal pump: hypothesised pathophysiological mechanism

The NDC mechanobiological model of breast inflammation builds on known science. Milk removal triggers milk ejection, which results in irregular alveoli contractions and ductal dilations. The mechanobiological model hypothesises that milk ejections downregulate stromal inflammation in two ways.

1. Milk ejections (waves of ductal dilations) create asynchronous and highly irregular waves or vibrations of pressure gradients within the stroma, acting as a stromal pump. This stromal pumping promotes venous and lymphatic drainage of the interstial tissue.1 Ducts dilate by up to 49% of their width again with milk ejection.

By allowing the ducts to open up, this stromal pressure pump

• Counteracts the compressive effects of high stromal tension upon the milk ducts, which

• Relieves the backpressure of high milk volumes in the alveoli, which

• Breaks the worsening cycle of inflammation in the surrounding stroma.

2. The vacuum application of milk removal (usually by the infant directly sucking but also mechanically) draws milk from the ducts and alveoli, at the same time as the ducts dilate and the alveoli contract, relieving high milk volumes and pressures within the alveoli.

You can find out about the NDC mechanobiological model of breast inflammation here.

This is why the NDC guidelines state that a woman with lactation-related breast inflammation be advised that milk needs to be removed from her affected breast very frequently and flexibly.

When a woman is removing milk mechanically

When a lactating woman removes her milk mechanically, that is, by pumping, it is important overall that she pumps milk that corresponds with her infant's needs. This is because pumping volumes of milk that are consistently more than her infant needs can place her at risk of mastitis. A cohort study of 346 breastfeeding women by Cullinane et al in 2015 showed that breastfeeding women who pumped a few times a day were at increased risk of mastitis. (The reasons for pumping were not investigated, though, and could be relevant to the findings.) From the mechanobiological perspective, milk production which exceeds the infant’s needs increases the risk of excessively high intraluminal pressures and breast inflammation.

Frequent flexible milk removal by hand expression or a pump is, however, a necessary response to breast inflammation if the woman has been predominantly mechanically expressing her milk. Any mismatch in supply needs to be addressed after the breast inflammation has resolved. The first task is to encourage frequent letdowns, at around the same frequency of pumping as had been used prior to the mastitis if the woman has been producing substantially more milk than her infant's caloric needs - but otherwise she may even increase frequency of pumping temporarily on the affected breast.

Recommended resources

Why advice to NOT change patterns of breastfeeding when a woman has mastitis risks worsened outcomes

The 12 steps of frequent flexible breastfeeding (which make life easier, not harder!)

Why most women don't need to worry about overstimulating their breasts or removing too much milk when they have mastitis or breast inflammation

Selected references

Cullinane M, Amir LH, Donath SM, Garland SM, Tabrizi SN, Payne MS, et al. Determinants of mastitis in women in the CASTLE study: a cohort study. BMC Family Practice. 2015;16:181.

Douglas P. Re-thinking benign inflammation of the lactating breast: a mechanobiological model. Women's Health. 2022;18:17455065221075907.

Douglas PS. Re-thinking benign inflammation of the lactating breast: classification, prevention, and management. Women's Health. 2022;18:17455057221091349.

Douglas PS. Does the Academy of Breastfeeding Medicine Clinical Protocol #36 'The Mastitis Spectrum' promote overtreatment and risk worsened outcomes for breastfeeding families? Commentary. International Breastfeeding Journal. 2023;18:Article no. 51 https://doi.org/10.1186/s13006-13023-00588-13008.