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Home » Bottle Feeding Breast Milk » Types of Breast Milk

Types of Breast Milk

By Amanda Glenn, CLC. Last Updated August 23, 2021. Originally Posted August 18, 2021.

You may have heard that there are all of these different types of breast milk – colostrum, transitional milk, mature milk, foremilk, and hindmilk. What exactly are these distinct kinds of milk? How are they different?

breast milk bags containing breast milk of varying shades of orange/yellow lined up flat on a counter with the darkest orange on the left and the lightest yellow on a the right with text overlay what are the different types of breast milk?

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Each of these types of breast milk is produced at different stages – both at different stages of breastfeeding, as your baby gets older, as well as at different points in a single feeding or pumping session.

Let’s talk first about the different types of breast milk that you see as your baby gets older.

Types of Breast Milk at Different Stages

Timeline charted titles Stages of Breast Milk - first bubble titled pregnancy (second trimester) and the second bubble is titled 2-5 days after birth. There is a line pointed to a position just before the second bubble labeled "birth". In between these two bubbles is the word colostrum. The third bubble is labeled 2-4 weeks after birth. In between these two bubbles is Transitional Milk. The fourth and fifth bubbles are labeled Weaning process, and in between the third and fourth bubbles is labeled mature milk, with the note that this stage. can last days or years. Between the fourth and fifth bubbles are the words involutional milk

There are four stages of breast milk that you’ll see as your baby gets older:

  • Colostrum is produced by your breasts during pregnancy up until two to five days after birth. (Some people leak colostrum during pregnancy and others don’t – both are normal.)
  • Transitional milk is produced starting from two to five days after birth, when your milk “comes in,” until two to four weeks postpartum.
  • Mature milk is then produced from two to four weeks postpartum until weaning. This phase can last anywhere from several days up to many years, depending on how long the parent removes milk from the breast.
  • Involutional milk is the milk that your breasts make at the very end of lactation.

Let’s talk about how these types of breast milk are different.

Colostrum

woman holding up two bottles she's pumped, each with a small amount of colostrum in them

As noted above, colostrum is the first milk that your breasts produce, and it is a thick milk that is ideal for newborns. Colostrum has 50 to 60 calories per 100 milliliters, or 15 to 17 calories per ounce. 

The macronutrients in colostrum break down as follows:

  • Carbohydrates: 50-62 g/L
  • Protein: 14-16 g/L
  • Fat: 15-20 g/L

From United Nations University:

Notably, colostrum is rich in secretory IgA, lactoferrin, Vitamin A, and sodium compared with mature milk, but it has relatively low concentrations of fat, lactose and Vitamin B1.

You may be able to “harvest” colostrum while you’re pregnant. More info on that here.

Mature Milk

two full bottles of mature milk on a white countertop in front of a Medela Sonata breast pump

I’m going to talk about mature milk next, even though transitional milk is produced after colostrum. That’s because the best way to describe the composition of transitional milk is to say it’s in between what we see in colostrum and in mature milk.

Mature milk is produced from two to four weeks postpartum until weaning. It contains 65 to 70 calories per 100 milliliters, or 20 to 22 calories per ounce.

Compared to colostrum, mature milk has increased carbohydrates and fats, but less protein:

  • Carbohydrates: 60-70 g/L
  • Protein: 8-10 g/L
  • Fat: 35-40 g/L

The composition of mature milk also changes throughout the first year. As time goes on, breast milk generally has less zinc, as well as other nutrients. However, some nutrients also increase over time.

Transitional Milk

As noted above, transitional milk represents the gradual transition between colostrum and mature milk.

Transitional milk starts when your milk comes in, and it ends when your milk becomes “mature” –  but there’s no set time that that happens. The exact timing varies from person to person, and the changes in composition change aren’t abrupt.

Instead, it’s a gradual change with increasing amount of fats and carbohydrates, and decreasing amounts of protein.

Involutional Milk

The last stage is involutional milk, which is the milk produced at the end of lactation.

This milk is lower in lactose and it has high concentrations of protein, fat and sodium.

Types of Breast Milk in a Pumping Session

In addition to the different types of breast milk that are produced over the first year, we also have different types of breast milk that occur over the course of a single feeding.

These are foremilk and hindmilk, and the difference between them is the amount of fat and fat-soluble components such as Vitamin A.

image of breast milk separated into a watery section on the bottom and a fatty section on top. The fatty section as an arrow pointing to it with the text hindmilk and the watery section has an arrow pointing to it with the text foremilk

Foremilk

In between feedings or pumping sessions, milk collects in the breasts. When your milk lets down, the fat, which is more dense, tends to stay stuck further back in the milk ducts.

This means that milk at the beginning of a pumping session is generally less fatty and more watery than later on.

Hindmilk

As the feeding or pumping session progresses, the fatty globules are dislodged and the milk that you are producing gets fattier.

Like transitional milk, which gradually becomes more mature over time, it’s not an abrupt switch. As time goes on, the composition of the milk slowly changes and starts to contain more fat.

Breast milk is breast milk

I wanted to provide this information about types of breast milk to give you more insight into what you’re producing, and to clarify any confusion from things you may have heard about your milk maybe not being fatty enough, or not being “good” anymore after a certain time.

However, there isn’t anything you necessarily need to do with this information or for you to be concerned about. (The potential exception to this is foremilk/hindmilk imbalance, which you can read more about here.)

Do you have any questions about the different types of breast milk over the stages of your baby’s life or over the course of a feeding? Feel free to ask in the comments!

References
  1. Bonyata, Kelly. “Foremilk and hindmilk – what does this mean?” Kellymom https://kellymom.com/bf/got-milk/basics/foremilk-hindmilk/
  2. Prentice, Ann. “Constituents of human milk.” United Nations University https://archive.unu.edu/unupress/food/8F174e/8F174E04.htm
  3. Su Yeong Kim, MD, Dae Yong Yi, MD, PhD. “Components of human breast milk: from macronutrient to microbiome and microRNA.” Korean Journal of Pediatrics https://www.e-cep.org/upload/pdf/cep-2020-00059.pdf
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Filed Under: Bottle Feeding Breast Milk

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Comments

  1. Jordan says

    February 22, 2022 at 9:39 am

    I have a large oversupply. I am almost 3 months pp and My baby is currently getting what I pumped 6 weeks ago. I’m making roughly 55-65 oz per day. Because of that, in just a couple of months, he may still be eating what I pumped in January. Is that okay?! Should we do something different to best meet his needs?

    Reply
    • Amanda Glenn, CLC says

      February 22, 2022 at 10:06 am

      Hi Jordan, no, that’s fine! Check out the first question/answer here for more info!
      https://exclusivepumping.com/exclusive-pumping-questions-lactation-consultant/

  2. ALEX says

    February 21, 2022 at 12:35 pm

    IS IT OKAY TO FREEZE EXTRA TRANSITION MILK AND FEED IT TO BABY IN THE FUTURE?

    Reply
    • Amanda Glenn, CLC says

      February 22, 2022 at 8:40 am

      Yes

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Amanda

Hi! I’m Amanda. I'm a Certified Lactation Counselor® and an experienced exclusive pumper. My goal is to help make exclusively pumping as easy as possible for you, so that you can enjoy your baby! This website is for educational purposes and should not be considered medical advice. Read More

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