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When Does Breast Milk Come In?
Updated on
September 1, 2023

When Does Breast Milk Come In?

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When Does Breast Milk Come In?.
When Does Breast Milk Come In?

Breastfeeding is a unique journey with many distinct parts, and your body producing milk is just the beginning. Whether you’re planning to exclusively breastfeed, exclusively pump or a combination of both, you’ve probably wondered when your body will actually start making milk. The timeline varies from person to person, and can be a bit confusing to navigate as a first-time parent.

We talked to Karrie Locher, a registered nurse and certified lactation counselor (CLC), to give you all the information you need.

When Does Milk Production Begin?

Milk supply doesn’t wait for baby’s arrival. Lactogenesis, or breast milk production, actually begins a bit earlier than most people may think. As early as a few weeks into pregnancy, your breasts will begin changing in preparation for milk production. This is triggered by rising levels of progesterone and estrogen which cause the number of milk ducts to increase and can leave your nipples and breasts feeling sore and sensitive.

Around weeks 16-22, your body will begin producing colostrum, a nutrient-dense thick golden milk. Often touted as “liquid gold”, this early milk is highly concentrated, packed with the perfect combination of nutrients, antibodies and proteins your baby needs after birth.

What are the Phases of Breast Milk Production?

Breast milk doesn’t just magically appear once you’ve given birth—there’s a lot going on behind the scenes leading up to its debut. Three phases of breast milk production span pregnancy to postpartum.

  1. Colostrum: According to Johns Hopkins, “Colostrum is a thick, rich milk that is high in nutrients.” It’s golden yellow in color and coats your baby’s brand new digestive tract in antibodies, helping to boost their immune system. It’s also easy to digest, helping baby pass that famous first sticky black poop called meconium.
  2. Transitional Milk: This stage of breast milk production occurs between 2-5 days after you give birth and is the milk that gradually replaces colostrum.
  3. Mature Milk: The last phase of lactogenesis, mature milk is whiter in color and higher in volume.

Can I Express Colostrum Before Giving Birth? What are the Benefits?

While it’s not totally necessary, there are benefits to expressing colostrum before birth.

“Collecting colostrum antenatally has many benefits, as it can be fed to babies immediately post birth (especially in unforeseen circumstances like NICU, low blood sugars, jaundice),” Locher says. Expressing colostrum is typically done after 36 weeks and it can be collected in breast shells or with a special collection kit. Always consult your doctor to get the green light before attempting to hand express colostrum as nipple stimulation can potentially induce labor.

What Does It Mean for Your Milk to Come In?

The phrase “milk coming in” refers specifically to the transition from that liquid gold colostrum to breast milk during the first few days after birth.

“After the birth of the placenta, a catalyst of hormone drops and surges occur as the driving force for ‘mature milk’ to come in a few days postpartum,” says Locher.

This usually happens between two and three days after your baby is born but can vary from person to person.

How Do I Know My Milk Has Come In?

Breast milk begins to transition from colostrum to what is called “mature” milk between three and five days postpartum, which Locher explains is “high in fat and sugar content and helps your baby start putting on more weight.”

How do you know your body has started producing this milk?

“Some signs may include engorgement (heavy + full breasts), swelling of the breast, skin tightening around the areola, flattening of the areola/nipple due to swelling [and] leaking milk just to name a few,” says Locher.

As your milk comes in some amount of breast fullness is normal and should be expected, but not everyone experiences engorgement. Another thing to note: the fullness of your breasts is not a good indicator of how much milk you’re producing. Not only do your breasts have a higher volume of milk, but “there is [also] a lot of fluid from the bloodstream and lymphatic system traveling there as well, which causes breasts to feel incredibly heavy, swollen, and sore,” says Locher.

How do I Know My Baby is Getting Enough Milk?

Whether or not you’re producing enough milk is a common worry among new parents (even if you’re on your second or third baby) but there are some ways to tell if your baby is getting enough milk. Here are a few clues that’ll help put your mind at ease:

Diaper output

In the first few days after your baby is born, the amount of wet diapers they have per day is a strong indication of whether they’re getting enough milk. According to American Pregnancy Association (APA), in the first few days you can expect 1-2 wet diapers per day and this should increase to 3-5 once your milk comes in.

Weight gain

This is probably the number one indicator. “Your baby will be followed closely by their care team post-birth to ensure they’re gaining weight appropriately,” Karrie tells us. While it’s normal for babies to lose 7-10% of weight after birth, anything beyond this can be a sign baby is not getting enough milk.

Observe how your baby is feeding

When your baby is nursing, look for “a nice deep latch on the breast without extreme pain, swallows while baby is nursing, baby waking to actively nurse well (not just sleeping at the breast each time),” says Locher.

Should I Pump to Relieve Engorgement?

If your baby is feeding well but you’re still feeling uncomfortable, it’s okay to express a little bit of milk to get some relief. The trick is knowing just how much to express.

“If we nurse our baby, but still feel engorged and decide we need to ‘empty’ the breast further, this signals our body that more milk is needed,” Locher explains, which could unintentionally lead to an oversupply. Breast milk production is based on supply and demand and it will take a little time for your body to figure out the right amount of milk it needs to produce for your baby.

What is the Best Way to Relieve Engorgement?

It can be a bit startling to experience your milk coming in for the first time. Your breasts might feel warm to the touch, super heavy and hard and they may even hurt a bit. Locher tips to relieve engorgement include:

  • Nursing your baby on demand
  • Using ice packs between feeds to help with inflammation
  • Taking a pain reliever like ibuprofen
  • Expressing just enough milk to remain comfortable

When I nurse, the opposite breast leaks. Will collecting this milk encourage an oversupply?

In the early weeks, your body, “tends to produce milk in abundance because it does not yet know how to meet baby’s specific demand,” Locher says. If you plan on going back to work you might want to take advantage of all of that “extra” milk and save it for your freezer stash. But will this lead to an oversupply? In short, it can–so don’t bust out your pump just yet. Locher recommends using milk collection cups versus pumping since they sit “passively in the bra [and] collect milk leaked, but do not add suction to pull out more milk than what drips out on its own.”

Many brands make milk collection cups, we especially like the ones from Haakaa and Elvie.

If you have pain with feeding or any concerns, a lactation consultant can provide personalized support in those first few days and weeks. Breastfeeding is a skill that both you and your baby are learning so take a deep breath, you’re doing great!


Karrie Locher, RN, CLC, is a mom of four and founder of Karing for Postpartum who has combined her personal and professional experience to help new parents feel confident and capable in both breastfeeding and parenting.

Briana Engelbrecht

Assistant Editor

Briana Engelbrecht is Babylist’s Assistant Editor, where she brings her passion for early childhood development and the perinatal period, plus experience as a mom of two to Babylist articles and guides. A former preschool teacher, she loves children’s picture books, cats, plants and making things.

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