The risks of expressing instead of breastfeeding

Why don’t I just express and not breastfeed?

Expressing and breastfeeding are very different, not just for the mother but for the baby too. Women who express regularly or exclusively are more likely to switch to infant formula, depriving their babies of the benefits of breastfeeding and breast milk. Expressing takes a lot of work and often takes longer than breastfeeding. If mothers don’t express effectively, they increase their risk of developing problems such as mastitis or an early return of periods. Alternatively, expressing can lead to an unusually large milk supply, which creates its own problems. Compared with breastfeeding, bottle-feeding with breast milk increases the baby’s risk of coughing, asthma, ear infections, overeating, and the teeth not lining up properly.

A) Comparing expressing and breastfeeding

For some mothers, occasional, temporary, or exclusive expressing may be critical to breastfeeding success. For babies, expressed breast milk has many benefits when compared to infant formula.

Most mothers see milk expression as an option to choose only when necessary but some prefer it to breastfeeding (Felice 2017; Jardine 2018).

Mothers faced with the choice of (a) breastfeeding, (b) breastfeeding and expressing, or (c) exclusively expressing need to consider that there are benefits to breastfeeding and risks to not breastfeeding and giving expressed breast milk.

B) The effect of expressing and storing on breast milk

Properly-stored breast milk is much better for babies than infant formula but it is slightly different from milk that is obtained directly from the breast. There is very little research on what effects these changes have on the health of babies.

Compared with the milk of breastfeeding mothers, the milk of mothers who only pump has larger amounts of potentially harmful bacteria and smaller amounts of health-promoting bacteria (Moossavi 2019). One theory for this difference is that breastfeeding allows bacteria from the baby’s mouth to have a beneficial effect on the types of bacteria in the breast and in breast milk. It is therefore not surprising that the gut bacteria of babies who receive pumped milk is less likely to contain health-promoting bacteria found in breast milk (Fehr 2020).

Processing (storing, refrigerating, freezing, and warming) of pumped breast milk may also deplete health-promoting bacteria.

Stored milk has less anti-oxidant activity than fresh milk. The longer the milk is refrigerated, the less the activity. Milk that is frozen has the least activity (Păduraru 2018).

Milk that is refrigerated is slightly more acidic and has a little less milk sugar (lactose) and protein (Ghoshal 2012). 

Freezing does not have a significant effect on the nutrients (protein, lactose, fat, energy) in breastmilk (Yochpaz 2020). However, it can reduce the activity of some immunological components such as immunoglobulin A and M and lactoferrin and will kill all live cells and health-promoting bacteria (Arroyo 2017; Pandya 2020; Peters 2016).  

Pandya SP, Doshi H, Codipilly CN, et al. Bacterial stability with freezer storage of human milk. J Perinat Med. 2020 Sep 14;49(2):225-228

Stored milk can develop a strong smell or taste and some babies may refuse to drink it.  

Stored milk can become contaminated if not properly handled.

C) The effect of not breastfeeding on the baby

Breastfeeding is very much controlled by the baby. The timing, duration, and amount of milk taken in are all controlled by the baby. Bottling is a very different process and may be caregiver-led. Compared with breastfeeding, bottle-feeding with breast milk may increase the risk:

  • Coughing and wheezing (Soto-Ramirez 2012)
  • Asthma (Karmaus 2018; Klopp 2017)
  • Eczema (Soto-Ramírez 2017)
  • Food allergies (Mathias 2019)
  • Ear infections (Boone 2016)
  • Poorer memory skills (Keim 2021; Pang 2019)
  • Overeating and obesity (Azad 2018; Disantis 2011; Li 2012)
  • The baby’s teeth not lining up properly (malocclusion)

Bottle-fed babies are harder to settle, since they don’t breastfeed to sleep. This can create more stress for both mother and baby.

Breastfeeding can be called timed nutrition (chrononutrition). The levels of some breast milk components change during the day and night. These variations may be providing nutrients when they are most needed by the baby, teaching and supporting the baby’s internal clock, and synchronizing the mother’s and baby’s body rhythms. Depending on the mother’s techniques, breast milk may be given away from the time it is expressed, disturbing the relationship between breast milk components and the time of day or night.

D) The effort of expressing

1) Obtaining milk

Expressing is a lot of work and often takes longer than breastfeeding. For example, in the second six months of life, breastfeeds during the day sometimes last only 5 to 10 minutes.

If you are pumping, you have to:

  • Get the pump.
  • Use the pump, which can take up to 20 minutes when double pumping or 40 minutes when single pumping.
  • Clean the pump parts.
  • Put the pump away.

Manual expression can take similar amounts of time and may be tiring. 

2) The additional effort needed to feed the baby

Once you have expressed, you still have to prepare the milk and feed the baby:

  1. Get the bottle or other feeding tool.
  2. Warm the milk.
  3. Feed the baby.
  4. Wash the feeding tool.
  5. Put the feeding tool away.

3) Other difficulties

Leaving the house is more complicated, since you have to:

  • Bring the pump.
  • Find a suitable place to express.
  • Safely store the milk.
  • Transport the milk.

In addition, if you have the baby with you, you also have to bring the milk and bottle or other feeding tools and keep the milk cold until you need to warm it and feed the baby.

This plan may break down if:

  • You forget any of these items.
  • Your pump does not work.
  • You cannot find a suitable place to express.
  • The milk:
    • Spills.
    • Is kept warm for too long.
  • Your plans change and you did not bring enough milk for the baby and can’t pump right when the baby needs milk.

These challenges are magnified if your family is in a crisis. It may leave your baby without appropriate milk.

E) The risks of poor breast emptying

A baby who can breastfeed effectively is often better at removing milk from the breast than the mother can by expressing (Prime 2012; Ramsay 2004). Some mothers may have even more trouble expressing if they are stressed or in pain.

Expressing also takes more time and effort than breastfeeding, resulting in irregular or infrequent expression.

Ineffective, infrequent, and irregular expression will cause excess milk to remain in the breast and over time the milk supply will decrease and the baby will require infant formula. Indeed, studies have shown that women who express regularly or exclusively are more likely to feed their babies breast milk for a shorter time and to begin using infant formula earlier than women who breastfeed most or all of the time and express occasionally or never (Bai 2017; Fan 2021; Keim 2017; Yourkavitch 2018).

A shorter period of breast milk feeding can affect the health and well-being of the mother and the babyPoor milk removal also increases the risk of various problems for the mother. For example, mastitis is more common in mothers who express (Foxman 2002). Over time, they may notice their periods return before six months after the birth.

F) The risk of creating a large milk supply

A few mothers are very sensitive to expressing and create an abnormally large milk supply. This can cause difficulties for mothers. Babies may also struggle if breastfeeding when the milk supply is very large.

G) The risk of pain with expressing

Expressing can be very helpful when managing breastfeeding pain but expressing can also be painful.  

Pumping can be painful for mothers and can be difficult to manage. Pumping will increase the length and diameter of the nipple, causing sensitivity and even pain. Pain can also be caused by poorly fitting breast shields or excess suction.

Manual expression can cause hand or breast pain or fatigue. It can make previous hand problems worse.

H) The environmental impact of expressing instead of breastfeeding

The environmental footprint of breastfeeding is the smallest, is larger when mothers express, and largest when infant formula-feeding.

Electric pumps are associated with waste plastic, waste electronics, energy demand, and the demand for critical raw materials. Expressed milk needs energy to be warmed. Plastics and latex used for bottles and teats or other feeding tools use energy for production and are then turned into waste.

The health challenges that may develop in mothers or babies and the increased likelihood of infant formula use increase the negative effect of expressing on the environment.


Arroyo G, Ortiz Barrientos KA, Lange K, et al. Effect of the Various Steps in the Processing of Human Milk in the Concentrations of IgA, IgM, and Lactoferrin. Breastfeed Med. 2017 Sep;12(7):443-445
Azad MB, Vehling L, Chan D, et al; CHILD Study Investigators. Infant Feeding and Weight Gain: Separating Breast Milk From Breastfeeding and Formula From Food. Pediatrics. 2018 Sep 24. pii: e20181092
Bai DL, Fong DY, Lok KY, et al. Practices, predictors and consequences of expressed breast-milk feeding in healthy full-term infants. Public Health Nutr. 2017 Feb;20(3):492-503
Boone KM, Geraghty SR, Keim SA. Feeding at the Breast and Expressed Milk Feeding: Associations with Otitis Media and Diarrhea in Infants. J Pediatr. 2016
Disantis KI, Collins BN, Fisher JO, et al. Do infants fed directly from the breast have improved appetite regulation and slower growth during early childhood compared with infants fed from a bottle? Int J Behav Nutr Phys Act. 2011 Aug 17;8:89

Fan HSL, Fong DYT, Lok KYW, et al. Association between expressed breast milk feeding and breastfeeding duration in Hong Kong mothers. Women Birth. 2021 Jul 5:S1871-5192(21)00110-4

Fehr K, Moossavi S, Sbihi H, et al. Breastmilk Feeding Practices Are Associated with the Co-Occurrence of Bacteria in Mothers' Milk and the Infant Gut: the CHILD Cohort Study. Cell Host Microbe. 2020 Jul 9:S1931-3128(20)30350-4 

Felice JP, Geraghty SR, Quaglieri CW, et al. "Breastfeeding" without baby: A longitudinal, qualitative investigation of how mothers perceive, feel about, and practice human milk expression. Matern Child Nutr. 2017 Jul;13(3)
Foxman B, D'Arcy H, Gillespie B, et al. Lactation mastitis: occurrence and medical management among 946 breastfeeding women in the United States. Am J Epidemiol. 2002 Jan 15;155(2):103-14
Ghoshal B, Lahiri S, Kar K, et al. Changes in biochemical contents of expressed breast milk on refrigerator storage. Indian Pediatr. 2012 Oct;49(10):836-7.
Jardine FM. Breastfeeding Without Nursing: "If Only I'd Known More about Exclusively Pumping before Giving Birth". J Hum Lact. 2018 Jul 1:890334418784562
Karmaus W, Kar S, Soto-Ramirez N, et al. Mixed infant feeding poses an increased risk for asthma in early childhood. J Allergy Clin Immunol 2018: 141(2); AB9
Keim SA, Boone KM, Oza-Frank R, et al. Pumping milk without ever feeding at the breast in the Moms2Moms study. Breastfeeding Medicine 2017:12(7);422
Klopp A, Vehling L, Becker AB, et al.; CHILD Study Investigators, Azad MB. Modes of Infant Feeding and the Risk of Childhood Asthma: A Prospective Birth Cohort Study. J Pediatr. 2017 Nov;190:192-199.e2
Li R, Magadia J, Fein SB, et al. Risk of bottle-feeding for rapid weight gain during the first year of life. Arch Pediatr Adolesc Med. 2012 May;166(5):431-6
Mathias JG, Zhang H, Soto-Ramierez N, et al. The association of infant feeding patterns with food allergy symptoms and food allergy in early childhood. Int Breastfeed J. 2019;14:43
Moossavi S, Sepehri S, Robertson B, et al. Composition and Variation of the Human Milk Microbiota Are Influenced by Maternal and Early-Life Factors. Cell Host Microbe. 2019 Feb 13;25(2):324-335.e4
Păduraru L, Dimitriu DC, Avasiloaiei AL, et al. Total antioxidant status in fresh and stored human milk from mothers of term and preterm neonates. Pediatr Neonatol. 2018 Dec;59(6):600-605

Pandya SP, Doshi H, Codipilly CN, et al. Bacterial stability with freezer storage of human milk. J Perinat Med. 2020 Sep 14;49(2):225-228

Pang WW, Tan PT, Cai S, et al. Nutrients or nursing? Understanding how breast milk feeding affects child cognition. Eur J Nutr. 2019 Feb 26
Peters MD, McArthur A, Munn Z. Safe management of expressed breast milk: A systematic review. Women Birth. 2016 Dec;29(6):473-481
Prime DK, Garbin CP, Hartmann PE, et al. Simultaneous breast expression in breastfeeding women is more efficacious than sequential breast expression. Breastfeed Med. 2012;7(6):442–447
Ramsay DT, Kent JC, Owens RA, et al. Ultrasound imaging of milk ejection in the breast of lactating women. Pediatrics. 2004;113(2):361–367
Soto-Ramírez N, Kar S, Zhang H, et al. Infant feeding patterns and eczema in children in the first 6 years of life. Clin Exp Allergy. 2017 Oct;47(10):1285-1298
Soto-Ramirez N, Karmaus W, Zhang H, et al. Modes of infant feeding and the occurrence of coughing/wheezing in the first year of life. Journal of Human Lactation 2012;29(1):71 – 80

Yochpaz S, Mimouni FB, Mandel D, et al. Effect of Freezing and Thawing on Human Milk Macronutrients and Energy Composition: A Systematic Review and Meta-Analysis. Breastfeed Med. 2020 Jul 17
Yourkavitch J, Rasmussen KM, Pence BW, et al. Early, regular breast-milk pumping may lead to early breast-milk feeding cessation. Public Health Nutr. 2018 Feb 13:1-11