When Does Breast Milk Come In? Experts and Moms on What It Feels Like

I distinctly remember the feeling of my milk letting down for the first time. Even though my boys are now 6 and 3––that tingly pins-and-needles sensation is one I’ll never forget. For years, I lumped that memory in with the moment my milk “came in”––but they’re not exactly the same thing.

“The expression milk ‘coming in’ is really misleading,” says Mindy Cockeram, IBCLC, lactation consultant and author of Breastfeeding Doesn’t Have To Suck! “Colostrum is milk,” she explains, noting that the body begins producing it at around the 16th week of pregnancy.

What actually happens in the first few days after birth is a process called secretory activation, when milk volume increases and colostrum gradually transitions to mature breast milk. For some, that shift comes with unmistakably fuller, heavier breasts. For others, the signs can be much more subtle.

So when does breast milk come in, exactly? And how can you tell whether yours is simply taking a little longer or truly delayed? Here, lactation experts take us through the typical breast milk timeline, what can affect it and what to actually do if your milk supply is slow to increase.

Key Takeaways

• When do you start producing breast milk? Your body begins making colostrum (the earliest breast milk) during pregnancy; milk is already present once baby is born.
• Milk volume typically increases within the first few days after birth. This process is called secretory activation. If that noticeable increase hasn’t happened by around 72 hours postpartum, it may be considered delayed.
• Signs your milk is coming in can look different for everyone. Fuller, heavier or firmer breasts are common as milk volume increases, but not everyone experiences dramatic fullness, leaking or engorgement.
• Frequent, effective feeding helps establish milk supply. Most newborns breastfeed about 8 to 12 times in a 24-hour period during the first few weeks.

When Does Breast Milk Come In?

Although people commonly talk about milk “coming in” after birth, breast milk (colostrum) production actually starts during pregnancy. After delivery, milk volume gradually increases as your body transitions through the early stages of lactation.

During pregnancy

Milk production generally begins around the midpoint of pregnancy, somewhere between weeks 16 and 22. At this stage your body is producing what’s known as colostrum—a yellowish milk that’s rich in protein and disease-fighting antibodies—which will serve as baby’s first food after birth. Some moms-to-be may even notice faint yellow or orange stains in their bra during the second or third trimester, a sign that their nipples are leaking colostrum. (If they never leak, that’s fine too.)

Right after birth

Breast milk changes gradually over the first days and weeks postpartum, moving from colostrum to transitional milk and then mature milk. Still, rather than happening at one exact moment, these phases overlap as milk volume and composition change to meet baby’s needs. It can even differ from child to child. “With my first, my milk came in literally overnight. I woke up in extreme pain and felt like I had rocks on my chest,” says Kristin R., a mom of two in New York. “With my second, it was much more gradual.”

Days after birth

Transitional milk typically comes in two to five days after birth. This is the period that’s most commonly referred to as “milk coming in”—as your body ramps up breast milk production to fill baby’s expanding belly.

Transitional milk will look thinner and whiter than colostrum, according to Dr. Sherry Ross, MD, a women’s health expert and author of She-ology: The Definitive Guide to Women’s Intimate Health. Bruno adds that it provides baby with more energy, as it’s higher in fat and carbohydrates. Transitional milk can last for up to 10 to 14 days after birth.

Weeks after birth

Toward the end of the second week, you can expect your production to move closer to the mature breast milk phase. Mature breast milk is the milk baby will continue to drink until it’s eventually time to wean.

“Breast milk composition changes throughout the breastfeeding relationship to match exactly what the baby needs,” explains Carrie Bruno, RN, IBCLC, a labor and delivery nurse and founder of The Mama Coach. “Breast milk contains two types of proteins: whey and casein. Over time, this ratio of casein and whey changes. Whey is high in immunoglobulins and easier to digest, whereas casein helps baby feel full longer. In the beginning, with colostrum, the ratio of whey to casein is 90:10, and after a month it’s 60:40. If Mom breastfeeds for over a year, it’s closer to 50:50.”

Signs Your Milk Is Coming In

When your milk does come in, you’ll probably know it. For many women, it’s a very distinct and new sensation. But, for others, it’s not as noticeable. Here are some signs to watch (and feel) for:

• Breast fullness: “Breasts physically fill with milk, which can feel heavy and sore. Breasts can feel hard to the touch, warm and tingly,” Bruno says. Cockeram agrees that breast fullness and firmness are common, but says the experience exists on a spectrum. “Most women notice hardness in the breast and a feeling of fullness,” she says. While some parents experience significant engorgement, others may not notice the classic signs at all. “My milk came in on day three, and then the engorgement started,” says Lauren B., a mom of three in Florida. “It peaked around nights five and six."
• Breasts leaking: “Mom may also notice her breasts leaking in between feeds,” adds nurse Bruno. This was also true for Cathryn J., a mom of three from Cheshire, Connecticut, who said “within days for each [of my children,] I had milk leaking everywhere.”
• Milk color: As your milk matures and production kicks into gear, it’ll likely look thinner and whiter (versus thicker, yellowish colostrum).
• Flattened areolas: Breast tissue swelling can make the areola look taut and flat.
• Baby will start to take longer gulps: Baby’s feeding patterns will likely also change. “Mom will start to notice baby staying longer at the breast, and be able to hear audible swallows of milk,” explains Bruno.

What to Do When Your Milk Comes In

Once your milk volume increases, your breasts may feel fuller, firmer or even uncomfortable for a few days. The goal is to keep milk moving while avoiding overstimulation that could make engorgement or oversupply worse.

Here’s what can help as your body adjusts to the increase in milk volume:

• Feed baby frequently: Continue feeding baby regularly and follow their hunger cues. Frequent milk removal can help relieve fullness and support milk production as your body adjusts to baby’s needs.
• Relieve engorgement as needed: If your breasts become very full, hand-expressing a small amount of milk before a feed can help soften the breast and make it easier for baby to latch, expert Bruno says. For Natalie V., a mom of four in Maryland, milk coming in meant significant engorgement and near-constant leaking. She relied on cold packs to help ease the discomfort. Bruno also recommends cold packs after feeds to help relieve discomfort.
• Pumping right away isn’t necessary for everyone: As an IBCLC, Cockeram recommends pumping in the first few days only if and when there’s a specific reason, like if baby isn’t latching well. Once milk volume has increased, routine pumping without a clinical need may stimulate your body to make more milk than baby needs. If you’re planning to build a freezer stash or introduce bottles later, Cockeram advises parents to wait until the three-to-four week mark to start stockpiling. “This also a good time to introduce baby to a (paced fed) bottle if warranted,” she adds.

Why Your Milk Might Be Delayed Coming In

There are several reasons secretory activation may be delayed, and many have to do with factors surrounding pregnancy, birth or your medical history. IBCLC Cockeram notes that cesarean delivery in particular is associated with delayed secretory activation. A number of factors may contribute, including the hormonal effects of surgery, anesthesia, maternal stress, IV fluids and delayed skin-to-skin contact. That doesn’t mean milk won’t come in after a C-section––it may simply take longer.

According to experts, other possible factors include:

• Being a first-time parent
• Improper latch
• Excessive blood loss during birth
• Postpartum hemorrhage
• Preterm labor
• Higher BMI
• Type 1 or gestational diabetes
• Thyroid abnormalities
• Certain birth interventions, including magnesium sulfate during labor
• An infection with fever
• Retained placental tissue
• Previous breast surgery (reductions or augmentation)
• Significant stress

What to Do If Your Milk Is Delayed

When my youngest was born, he needed some formula supplementation around his second night at home due to jaundice while my milk production caught up with his needs. I was nervous about what that might mean for our breastfeeding journey, but he was more content after feeds––and once my supply increased, I was able to nurse him successfully. In any case, the right next step depends on what may be causing the delay and how well baby is feeding.

• Seek professional support: If your milk volume hasn’t noticeably increased by around 72 hours postpartum, or you’re concerned baby isn’t getting enough milk, it’s worth checking in with a lactation consultant or healthcare provider. Together, you can build a plan for how to help your milk come in. “Sometimes, while moms wait for their milk to come in, there’s a need for supplementation,” Bruno says.
• Feed frequently and focus on effective milk removal: Cockeram recommends feeding baby frequently in the early days—at least eight times in 24 hours—and offering both breasts. “The best way to make milk come in faster is to remove milk consistently from both breasts,” she says. Skin-to-skin contact can also help stimulate oxytocin and encourage baby to feed.
• Watch baby’s output: Wet and dirty diapers are among the most useful clues that baby is getting enough milk in the first several days. “What goes in must come out,” is Cockeram’s mantra as a lactation consultant. While frequent feeding and cluster feeding can be normal—particularly around the second night after birth—a lack of expected wet or dirty diapers warrants a call to baby’s pediatrician or a lactation consultant.

To Sum It Up

Your body has been producing breast milk––colostrum––since pregnancy. What typically happens in the first few days after birth is a significant increase in milk volume as secretory activation gets underway. And there isn’t one universal way the shift looks or feels—it may be sudden and obvious or much more gradual and low key. Either way, frequent, effective feeding will help support milk production, but if your milk seems to be delayed, feeding is painful or you’re concerned baby just isn’t getting enough, reach out to your healthcare provider or a lactation consultant for support.

How We Developed This Article

We know how stressful the first few days and weeks of breastfeeding can be. You’re wondering if you’re making enough milk to keep baby healthy and happy. To help demystify exactly when breast milk comes in we spoke with two lactation experts about secretory activation, delayed milk production and what to expect postpartum. We also interviewed real moms who shared their firsthand experiences of what milk coming in felt like for them. After editing, this article was vetted through fact-check and reviewed by our pediatrician medical reviewer. Learn more about how we ensure the accuracy of our content through our editorial and medical review process.

About the author: Christine Carpenter is a contributing writer and editor for The Bump and a mom of two boys. Her own feeding experiences looked very different. She exclusively pumped for her first son and breastfed her second for two years. She has written extensively about pregnancy, postpartum and infant feeding, and brings both personal experience and a research-driven approach to these topics.

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.