Milk Supply 101

Let’s chat about milk supply basics - how milk is made, how supply is established, and what keeps it going.

Knowing the key players in milk making can help you understand your body and your baby.

And before we get caught up in increasing or decreasing milk supply, let’s discuss how and when milk is made.

Milk Making In Pregnancy 

Assuming the absence of hormonal issues, a mother’s body begins to make colostrum around 20 weeks of pregnancy. A mother may notice leaking, fullness in her breasts, and an increase in cup size. Mom’s body is hard-wired to start this process of milk synthesis in pregnancy, but will stay in the pregnancy- mode of milk making, or Lactogenesis I, until the delivery of the placenta. 

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Milk Making After Delivery

After the delivery of the infant and the placenta, the mother’s body switches from pregnancy-mode to milk-making mode, or Lactogenesis II. At this point, milk making is a hormonally-driven process. Once the placenta is delivered, the hormone progesterone takes a steep dive, which lays the space for prolactin to make a steep climb. Prolactin is a hormone that plays a critical role in milk making. 

Regardless of if a mother is breastfeeding or not, her body will go through Lactogenesis II.  

Around day 2-3 of the infant’s life, a mother’s volume in breastmilk will increase, commonly referred to as “milk coming in.” Milk making is still hormonally driven at this point, which is one of the reasons why offering frequent feedings or frequent stimulation is crucial to establishing milk supply. 

Around 6 weeks after delivery, Lactogenesis III occurs, which is where a mother’s  milk supply switches from being an endocrine-driven process (where a mother’s hormones drive the process) to an autocrine- driven process. Lactogenesis III is where milk maintenance occurs, and frequent milk removal is the driving force behind changing milk supply output. In this stage of milk-making, hormones still play a role in the milk supply equation, but less so. 

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Variations in Milk Supply:

One of the amazing things about breastfeeding is that a mother’s body and a baby’s needs work in tandem. A mother’s body will receive the signal from the baby’s demand, and will adjust the milk supply to meet it. This of course is assuming there are no underlying issues and risk factors for either the mother or infant.

Let’s look at a few reasons why this feedback loop may not work as we expect:

1. Low supply

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Low supply is when the baby’s demand is greater than milk output. 

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This can happen for a variety of reasons, such as:

• Ineffective milk removal (i.e. poor latch, incorrect flange size, weak suck)
• Infrequent milk removal (i.e. skipped feedings, giving a bottle without pumping to stimulate the breasts)
• Underlying hormonal issues for the mother (i.e. PCOS)
• Previous breast surgery
• Endocrine disorders (i.e. hypothyroidism)
• Certain medications, including estrogen-containing birth control. 

Of course, none of these means that you will have low milk supply, it’s factors that can put a dyad at risk. As always, seek the support of your healthcare provider and a trusted lactation professional if you are concerned. 

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Recommendations:

• Breastfeed your infant frequently, and follow their cues.
  
  • Newborns need to be fed a minimum of 8-12 times in 24 hours. 
    
    • Frequent stimulation =  more demand = more milk
• Make sure your infant is latching well
  
  • A good latch has both nipple and areola inside the infant’s mouth, is asymmetric, and is not painful to the mother.
• If  your infant is unable to feed well at the breast, then pump or hand express to stimulate your breasts and remove milk.

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2. Oversupply

Oversupply is when milk output is greater than the baby’s demand.

• The most common reason why this occurs is because the breasts are too stimulated. For example, if a mother is breastfeeding her baby, then pumping afterwards (without being directed by her lactation provider), then her body is making more than what the baby needs. 
• While it may feel awesome to have a large freezer stash of milk, oversupply can put mothers at greater risk for discomfort from engorgement, clogged ducts, and mastitis. 

Recommendations:

• A technique called block feeding is generally recommended in the presence of oversupply. With block feeding, a mother feeds on only one breast for 3-4 hours, then for the next 3-4 hours, feeds from the other breast.
  
  • For example, for any feedings from 7am-11am, the mother expresses milk from the right breast only. Then from 11am - 3pm, the mother expresses milk from the left breast only.
• Usually, if a mother is pumping on top of feeding her infant at the breast, we will establish a plan to decrease pumping. 
• When managing oversupply, we want to manage and prevent engorgement, clogged ducts, and mastitis. 
  
  • Use cold packs in the presence of engorgement to decrease inflammation.
  • Speak with your provider about using NSAIDs (i.e. ibuprofen) to decrease inflammation.
  • Avoid massaging a hard spot, as it can cause more inflammation and discomfort. 

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If you feel you are struggling with either oversupply or undersupply, please consult with a trusted lactation provider who can work with you. Because every mother and every baby is different, your care should be tailored to you. 

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References:

Berens, Pamela, and Miriam Labbok. “ABM Clinical Protocol #13: Contraception during Breastfeeding, Revised 2015.” Breastfeeding Medicine, vol. 10, no. 1, Feb. 2015, pp. 3–12, abm.memberclicks.net/assets/DOCUMENTS/PROTOCOLS/13-contraception-and-breastfeeding-protocol-english.pdf, https://doi.org/10.1089/bfm.2015.9999.

Johnson, Helen M., et al. “ABM Clinical Protocol #32: Management of Hyperlactation.” Breastfeeding Medicine, vol. 15, no. 3, 1 Mar. 2020, pp. 129–134, https://doi.org/10.1089/bfm.2019.29141.hmj.

Lauwers, Judith, and Anna Swisher. Counseling the Nursing Mother : A Lactation Consultant’s Guide. Burlington, Ma, Jones & Bartlett Learning, 2021.

Pados, Britt Frisk, and Lindsey Camp. “Physiology of Human Lactation and Strategies to Support Milk Supply for Breastfeeding.” Nursing for Women’s Health, vol. 28, no. 4, 1 July 2024, https://doi.org/10.1016/j.nwh.2024.01.007.

USDA. “Low Milk Supply | WIC Breastfeeding.” Wicbreastfeeding.fns.usda.gov, wicbreastfeeding.fns.usda.gov/low-milk-supply.

Wilson-Clay, Barbara, and Kay Hoover. The Breastfeeding Atlas. Manchaca, Texas, Lactnews Press, 2022.

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‍Disclaimer: This information provided in this blog article is for educational purposes only and is not intended as medical advice. While we strive to provide accurate and up-to-date information, it is important to consult with your qualified healthcare professional before making any decisions about supplementation or addressing concerns about your baby's weight gain. This information is not a substitute for professional medical consultation, diagnosis, or treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here. For further information, please consult with a pediatric healthcare provider or visit reputable medical sources such as the American Academy of Pediatrics or the World Health Organization