When Does Breast Milk Come In? Colostrum to Mature Milk

In the first days after birth it can feel like nothing is happening, and it’s easy to worry that you have no milk. But you do. Your body has been making colostrum for months, and it’s exactly what your newborn needs while your full milk supply gets going.

Here’s what happens, when to expect your milk to come in, how to tell when it has, and what to do if it seems slow.

Colostrum: milk from pregnancy

Your breasts start preparing for feeding early in pregnancy. Cleveland Clinic explains that the first stage of milk-making begins around week 16 of pregnancy and that your body is making colostrum by about midway through. Some people notice small drops or crusty yellow spots on their bra in the later months; others don’t, and both are normal.

After birth, colostrum is your baby’s first food. The CDC describes it as thick and yellowish, rich in nutrients and substances that support your baby’s immune system. The amounts are small at first and increase gradually over the first couple of days. That’s normal. Your newborn’s stomach is tiny, and frequent small feeds are the design, not a shortfall.

When does breast milk come in?

Delivering the placenta triggers a sharp drop in pregnancy hormones, and prolactin takes over. That shift starts the next stage, called lactogenesis II (also known as secretory activation), when milk volume rises sharply.

Stage	When	What you’ll notice
Lactogenesis I	From around mid-pregnancy until a few days after birth	Colostrum, in small amounts
Lactogenesis II	Usually 2–5 days after birth, often around day 3	Breasts feel fuller, heavier and warmer; milk becomes thinner and whiter
Ongoing (lactogenesis III)	Once mature milk appears, near the end of week 2 (AAP)	Supply adjusts to how much milk your baby removes

The AAP describes “milk coming in” as the start of transitional milk, about two to five days after birth. The CDC says most mothers’ milk comes in by about 3 days after birth, and that it may take longer for first-time mothers. Your milk doesn’t switch overnight: colostrum gradually changes to transitional milk and then mature milk over the first couple of weeks.

Signs your milk has come in

• Your breasts feel fuller, firmer, heavier or warmer
• Your milk looks thinner and whiter, and you may see it on your baby’s lips or leaking
• You hear more frequent gulping and swallowing during feeds
• Your baby’s diapers change: more wet diapers, and stools turn from dark, sticky meconium to green and then yellow
• Your baby may want to feed even more often for a day or so

For some people the change is gentle. For others the breasts become very full and tight. If yours are hard and painful, see our guide to breast engorgement.

What can delay milk coming in

Milk coming in at around 72 hours (3 days) or later is often described as delayed. It’s common, and it doesn’t mean you can’t breastfeed. Research has linked delayed onset with:

• First baby
• Cesarean birth
• Diabetes, including gestational diabetes, and a higher body mass index (BMI) before pregnancy
• Putting your baby to the breast later: in one Toronto study, first breast contact 2 or more hours after birth (compared with within 1 hour) was linked to delayed onset
• Stress and low mood: Johns Hopkins lists severe stress, and in one study of women who had a C-section, higher depression screening scores were linked to delay
• Fewer feeds in the first 48 hours (also from the C-section study)
• Heavy bleeding after birth (mention it to your doctor if your milk doesn’t come in and you have heavy or prolonged bleeding)
• Thyroid conditions, and infection or illness with fever (Johns Hopkins)

The evidence is mixed. In that same Toronto study, diabetes and BMI measures were not significantly linked to delay. Johns Hopkins notes that when a health condition is involved, the large increase in milk can sometimes be delayed until 7 to 14 days after birth.

What to do while you wait

1. Feed early and often. Aim for 8–12 feeds in 24 hours, as the CDC advises, starting in the first hour if you can. Every feed sends a signal to make milk.
2. Spend time skin to skin. It helps your baby wake for feeds and supports milk-making hormones.
3. Check the latch. Ask your nurse or a lactation consultant to watch a feed. A deep latch moves more colostrum. Our guide on how to breastfeed covers latch and positions.
4. Hand express. If your baby is sleepy or not latching well, hand express colostrum into a spoon or syringe and feed it to your baby. This also stimulates supply.
5. Pump if you’re separated. If your baby is in the NICU or can’t feed at the breast, start expressing as soon as you can after birth, as often as your baby would normally feed (8–12 times in 24 hours, per the CDC).
6. Track diapers. The CDC’s minimums are 1 wet diaper on day 1, 2 on day 2, 5 on day 3 and 6 from day 4.

If your baby needs a supplement for medical reasons, ABM Protocol #3 says your own expressed milk is the first choice, then donor human milk where available, and formula can be used when needed. Talk with your baby’s doctor and keep expressing to protect your supply. For more ways to build supply, see how to increase milk supply.

Collecting colostrum before birth

Some people hand express and store colostrum in the last weeks of pregnancy so it’s ready if their baby needs extra milk, for example with diabetes in pregnancy or a planned C-section. One NHS guideline (NHS Greater Glasgow and Clyde) recommends starting at 36–37 weeks and using hand expression only.

It isn’t right for everyone. That guideline advises against it with threatened preterm labor before 36 weeks, a cervical stitch, placenta previa, vaginal bleeding or ruptured membranes in the current pregnancy, or too much amniotic fluid (polyhydramnios), among other conditions. Only collect colostrum before birth with your OB-GYN or midwife’s approval, and stop and call them if you get regular or painful contractions.

When to call a doctor or lactation consultant

Contact your baby’s doctor and a lactation consultant if:

• Your breasts haven’t felt fuller by about day 4 or 5
• Your baby has fewer wet or dirty diapers than the CDC minimums
• Your baby keeps losing weight after day 5, or isn’t back to birth weight by 10–14 days
• Your baby looks yellow
• Feeding is painful

You can find help through our breastfeeding support page, and learn more about how supply works on our milk supply hub.