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Colostrum vs. Milk: Key Differences and Benefits for Your Newborn

Person pouring breast milk into baby bottles

If you are planning to breastfeed, it is important to learn about the different kinds of milk your breasts will make. As your milk is coming in, it starts out as colostrum and transitions into mature breast milk over the first ten to fourteen days. There are many differences between these two kinds of milk. Let’s explore these differences to help you understand how to best feed your newborn.

What is Colostrum?

Often called “pre-milk,” colostrum is the nutrient rich early milk produced by your breasts towards the end of pregnancy. When your baby is first born, it starts to get released from your breasts and provides everything your newborn needs for the first few days. If you are unable to breastfeed or choose not to, you can hand express colostrum to release it. Colostrum is important for all babies but especially those who are born prematurely. 

It is thick and sticky and usually looks clear, white or yellow. If it looks more yellow than mature breast milk it’s because of high concentrations of Vitamin A and other antioxidants called carotenoids. 

Because colostrum is sticky, it coats your baby’s bowels to help protect them from absorbing bacteria and other germs and reduces inflammation. It also kills germs that can be harmful to your newborn. Because of the small amount of milk sugar, called lactose, colostrum can act as a mild laxative to clear your baby’s early stool, called meconium. The lactose can also prevent low blood sugar.

What is Colostrum Made of?

Colostrum contains high levels of protein, vitamins, minerals and immune cells that produce antibodies. The antibodies help your baby’s immune system fight off infection until your baby is able to produce their own antibodies. Colostrum also has small amounts of sugar and fat. 

Even tiny amounts of colostrum contain a lot of nutrients, so your baby doesn’t need a big volume of it to get what they need at first. 

What Kinds of Nutrients are in Colostrum?

Colostrum is concentrated with the following components:

  • High amounts of Vitamin A, Vitamin B12, Vitamin K

  • Magnesium

  • Zinc

  • Copper

  • High amounts of protein

  • Small amounts of lactose

  • Developmental factors that help your baby’s growth

  • Epidermal growth factor

  • Growth factors: TGFβ1 and TGFβ2 

  • Immunologic components that help prevent infections and modulate the immune system

  • Immunoglobulin A

  • Interleukins 6, 8, 10, and 13

  • White blood cells

  • Lactoferrin 

When Do You Start Leaking Colostrum?

When you are pregnant, your breasts start producing colostrum at around 12-18 weeks. Your breast will continue to produce it for the first few weeks after your baby is born. Nursing your newborn within the first hour of birth provides them with a large volume of colostrum If your baby is unable to nurse in the first few hours, you can hand express it and feed it to them with a dropper or bottle. Hand expressing is usually more effective than pumping colostrum. 

How Much Colostrum Does a Newborn Need to Eat?

At birth, your newborn’s stomach is as tiny as a marble. It can hold about 5 ml or 1 teaspoon of colostrum at a time. For the first day, they usually drink a total of one ounce of colostrum, divided over eight to ten feedings. Over the course of the first week, the volume of colostrum will increase and turn into transitional milk. After the first week, your baby’s stomach will continue to stretch as your supply turns from transitional milk to mature breast milk to meet their needs.

Why is Colostrum Important for a Newborn?

  • Because it is full of nutrients, protein, immune cells and growth factors, colostrum has everything your newborn baby needs for the first few days of life. It also flows slowly and in small amounts from your breasts, making it easier for your baby to learn how to suck and swallow. Colostrum is particularly important for babies who are born preterm.

Here are some of the benefits of colostrum for your newborn: 

  • Provides ideal nutrition

  • Easily digestible

  • Supports the immune system

  • Coats the intestines to prevent harmful microorganisms, such as bacteria and viruses, from being absorbed by the gut

  • Can act as a laxative to clear early poo, called meconium

  • Reduces the risk of jaundice

  • Reduces the risk of low-blood sugar in full-term babies

What is the Best Way to Express Colostrum?

Colostrum harvesting is different from extracting transitional or mature breast milk. Because it is stickier and is made in such small amounts, it is easiest to remove it from your breasts using hand expression. It is easy to learn and can yield the biggest volume. 

It is difficult to remove colostrum from your breasts using an electric pump, but an electric pump can be helpful once your transitional and mature milk comes in. 

How is Colostrum Different than Milk?

Colostrum is thick, sticky and either clear, white or yellow. It is produced in the first few days after your baby is born in very small amounts. After 3 to 4 days, colostrum begins to change into transitional milk. This milk is whiter and thinner than colostrum, and the amount increases every day. As your breasts ramp up the milk production, they usually become more firm, tender, and full. Sometimes they can even become engorged

After 10 to 14 days, transitional milk changes to mature milk. Mature milk is thicker than transitional milk, whiter, and is produced in greater volume. It also has different nutrients and living cells. 

Compared to colostrum, mature breast milk has:

  • Half as much protein

  • Higher fat

  • Higher lactose (milk sugar)

  • More water

  • Four times less zinc

  • Fewer immunoglobulins

  • Other cellular elements, like stem cells

When Does Mature Milk Come In?

For the first few days your breasts make colostrum in small amounts (20-40 ml a day). 

From day 3 to day 14, your breasts make transitional milk. This milk changes in consistency and volume until it becomes mature breast milk.

Here is the average volume of transitional milk most moms make:

  • Day 3-4: 300 to 400 ml a day

  • Day 5: 500ml a day

  • Day 10-14: 800 ml a day

By day 10 to 14, your breasts should be making mature breast milk, usually between 800 to 1000 ml a day. The total amount of milk a mom can produce varies widely. It can be anywhere from 800 mls a day to thousands of mls a day.

By the time your baby is four weeks old, the total volume of milk they per day stays the same, even as they are growing. Your baby may nurse less often as they get bigger, but they will also take in more milk with each nursing session. 

Frequently Asked Questions

Does Leaking Colostrum Mean Labor is going to happen soon?

Colostrum is produced by your breasts starting at 12-18 weeks of pregnancy. It is normal to leak colostrum during pregnancy, even as early as the second trimester. The leakage can look fluid or dried onto the nipples. If this happens, you can use breast pads. However, leaking colostrum does not mean labor is coming. 

Is it easy to pump colostrum?

Colostrum is sticky and produced in small amounts, so it is hard to remove it from your breasts using a breast pump. Most moms have better results when they hand express colostrum, especially during the first hour after the baby is born. 

What happens if I don’t make colostrum?

It is rare that moms don’t produce colostrum. If this happens it is likely to do to a medical issue or medication. Most moms produce at least enough colostrum for the first few days. If your breasts aren’t leaking, you can hand express to get the process started. Remember, your baby only needs one teaspoon of colostrum the first day and a few teaspoons a day by day 3.

When is the best time to express colostrum?

The best time to express colostrum is the hour after your baby is born. That is when most moms produce the most volume. That’s also why it is wonderful if you are able to nurse your baby right away. 

What can I give my baby if my colostrum doesn’t come in?

If your colostrum doesn’t come in, you can give your baby formula or donated milk from a milk bank.


Colostrum is all your baby needs in the first few days of life. It is densely packed with nutrients, growth factors and immune cells. Learn the differences between colostrum and milk so you know how to properly feed your baby. 

Reviewed by:  Linda Dahl, MD


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