Here's exactly how your body makes milk (spoiler: it's freakin' amazing!)

The wondrous process of milk production starts when you're just 6 weeks pregnant and carries on until you stop nursing. Here are all the incredible details.

Here's exactly how your body makes milk (spoiler: it's freakin' amazing!)

Photo: iStockphoto

Whether you're thoroughly experienced or just starting out, breastfeeding a baby can be a beloved (though not always easy!) part of motherhood. While getting the hang of nursing can take some time, for both mom and baby, once you find your rhythm it often becomes an established routine. But have you ever wondered how your milk is actually made? From the start of milk production at just six weeks pregnant to your baby's ability to draw it out, here's a breakdown of the wondrous process.

Your milk during pregnancy

When you're six weeks pregnant, hormones tell your body to turn glandular tissue into milk-making cells called lactocytes. These cells line the alveoli, balloon-like sacs attached to ducts in clusters. By the 32-week mark, lactocytes start producing colostrum to fill the alveoli.

Your milk at birth

Once your baby is born and the placenta is delivered, hormones tell your body it's time to turn that colostrum into mature milk; this transformation typically finishes around day two to four. To keep the milk supply going, your baby needs to nurse or you need to pump—otherwise it will go away within a day or two.

Your milk in the following months

Hormones are always part of the milk-making process, but starting at day 10, production will begin to gradually rely more heavily on supply and demand—the more the baby nurses, and the more they do so effectively and fully drain the alveoli, the more milk will be produced.

Diagram of breast

How your baby gets milk

First, your baby's tongue presses upward on your breast, which signals the release of oxytocin. The oxytocin causes breast tissue to contract, causing a pressure that squeezes milk-filled alveoli and lets milk down into the ducts and out the nipple. In the weeks after your baby is born, your breasts might feel fuller before a feed than after, but that will stop in a few months when your supply regulates.

How do I know if my baby is getting enough milk?

There is no way to tell how much milk you're making—you can't pump and judge base on what comes out, because your body may not respond to a machine as it would to a real baby. Instead you need to look to your little one for clues. If your baby is gaining weight, has at least six wet diapers a day from day six on and is generally happy at the breast, they are likely getting enough milk.

5 fascinating facts about milk production


1. The composition of your milk changes based on your baby's needs. Factors like the frequency of feeds, the time of day they eat and what's in their saliva tell your body what's needed, and the amount of fat, nutrients and antibodies in the breastmilk adjust accordingly, says Ashley Pickett, a lactation consultant in Toronto.

2. People once believed it was important to keep your baby at the breast for a certain amount of time to ensure they got enough hindmilk, the fattier milk at the end of a feed, compared to foremilk, which is at the beginning. But Pickett says this is no longer a concern—as long as you let your baby feed as often and for as long as they want, they will get the composition of milk they need.

3. Oversupply is rare, so if your baby chokes, sputters or gags when your milk comes in, it's probably due to an overactive letdown, in which the baby can't handle how quickly the milk is coming out, says Pickett. "They might come off the breast upset; it feels overwhelming to them." Pickett suggests making sure your baby is latching well to better handle the fast-flowing milk.

4. Babies who have issues with latching (because of a tongue-tie, for example) are still able to bring in milk in those early days. However, if those milk-making lactocytes are not used to their potential, they will start to die off, which could decrease your milk supply, as the remaining cells need to work harder to produce the milk.

5. The first letdown of a feed is super sensitive to triggers like sound, touch and smells. That's why some women find themselves leaking milk when they hear another baby cry.


Read more: Breastfeeding my three-year-old is an act of resistance When you’re plus-size, you get a lot more side-eye for breastfeeding in public

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Alex is a Toronto-based writer and editor. She currently works as a managing editor for Mind Over Matter magazine. Her work can also be found in publications like The Globe and Mail, Chatelaine, and The Walrus.