How Breastmilk Production Works

A lactating breast has ducts that carry milk from the alveoli (milk producing cells) to the nipple, where it is released through several holes. Oxytocin and prolactin are the two main hormones involved in milk production. Oxytocin triggers milk release and promotes bonding, while prolactin creates the milk.

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Milk production begins hormonally during pregnancy, with colostrum usually produced halfway through. After birth, colostrum transitions into mature milk at around day 3-5, and milk production begins to be driven by supply and demand (also known as lactogenesis III). Effective milk removal, typically 8-14 feedings per day, supports milk production.

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The Feedback Inhibitor of Lactation (FIL), a protein in breast milk, signals the body to slow down milk production when breasts are full. Cluster feeding, especially in the evening, helps to stimulate milk supply, and growth spurts may lead to more frequent feeding.

Milk storage capacity varies, and responsive feeding is key to maintaining milk supply. Even if a mother has a lower storage capacity, frequent feeding supports her baby’s growth and ensures a steady supply. Responsive feeding also helps babies feel secure and nourished. If a baby isn’t feeding frequently enough or isn’t removing milk properly (due to issues like a poor latch or tongue tie), it can lead to blocked ducts. If these blockages aren’t cleared quickly through breastfeeding or pumping, milk can leak into surrounding tissues, causing inflammation known as mastitis.