What does meconium look like?

Meconium is dark greenish-black, thick, sticky, and tar-like - similar to motor oil or black licorice in texture. It has almost no smell. It's made up of everything the baby swallowed in the womb: amniotic fluid, intestinal cells, mucus, and bile. It looks alarming but is completely normal.

When should a newborn pass meconium?

Most newborns pass meconium within the first 24 hours after birth, and nearly all do within 48 hours. If your baby hasn't had a bowel movement within 48 hours, your pediatrician needs to know - it can be a sign of a blockage or condition like Hirschsprung's disease.

How long does meconium last?

Usually 1 to 3 days. By day 2-3, poop starts transitioning to greenish-yellow 'transitional stools.' By day 4-5, it shifts to milk stool - yellow and seedy if breastfed, tan if formula-fed. If you're still seeing black tarry stool after day 4 or 5, mention it to your doctor.

What are transitional stools?

Transitional stools are what comes between meconium and regular milk poop - they appear around days 2-4 and look greenish-yellow or brownish, with a thinner consistency than meconium. They're completely normal and mean the digestive system is starting to process milk instead of just clearing out womb contents.

What if baby pooped meconium before birth?

Meconium-stained amniotic fluid (when baby passes stool in the womb before delivery) is something your delivery team watches for and manages at birth. It's different from the normal meconium your baby passes in the first days. If your doctor mentioned meconium at delivery, they will have already assessed whether any intervention was needed.

Meconium: What Baby's First Poop Looks Like and When to Worry

You just had a baby. You're running on zero sleep. And then you open the first diaper and find something that looks like black tar. Thick, dark greenish-black, sticky enough to require five wipes.

This is meconium. It's completely normal. And it disappears within a few days.

What meconium actually is

Your baby spent 9 months in the womb swallowing amniotic fluid. Meconium is what built up in the intestines from all of that - amniotic fluid, mucus, bile, shed intestinal cells, and fine hair called lanugo. It's been accumulating since around 16 weeks of pregnancy.

The result: a dark greenish-black, tar-like substance with almost no smell. It's sterile (unlike later poop), which is why it doesn't have that characteristic odor. The consistency is famously difficult to wipe off - it sticks like glue.

Pro tip: a small amount of petroleum jelly or coconut oil on the skin before the first few diapers makes cleanup much easier.

The normal timeline

Day 1: First meconium within 24 hours of birth. Usually happens within 8-12 hours for most babies.

Days 2-3: Transitional stools appear. These are the intermediate stage - greenish-yellow or brownish, thinner than meconium. It means the gut is starting to process milk rather than clearing out womb contents.

Days 4-5: Milk stool arrives. If breastfeeding: yellow, seedy, loose, mildly sweet-smelling. If formula: tan to light brown, firmer, more pungent. Once you see this, meconium is done.

One thing to watch for

If your newborn hasn't passed meconium within 48 hours of birth, tell your pediatrician or the hospital team the same day.

Delayed meconium can be a sign of a blockage or a condition called Hirschsprung's disease, where a section of the colon is missing the nerve cells needed for normal movement. It's rare, but it's the reason hospitals track the first stool carefully.

Most of the time this is just a slightly slower-than-average start - but it needs to be checked.

Black stool after the newborn period

Once meconium has passed and your baby is on milk stool (usually by day 5), black tarry stool should not come back. If you see it after the first week, that's a different situation entirely. Black tarry stool later in infancy (called melena) can indicate bleeding from the upper gastrointestinal tract and needs immediate medical evaluation. Call your pediatrician right away or go to the ER.

This is different from dark green stool - dark green is common and often caused by iron in formula. True black and tarry after the newborn period is not.

When breastfeeding is going well

The transition from meconium to yellow milk stool is one of the clearest signs that breastfeeding is established. For a full guide to what milk stool should look like for breastfed vs. formula-fed babies, see breastfed vs. formula-fed baby poop. If you're still seeing dark transitional stools by day 5 or 6, it may mean baby isn't transferring enough milk - worth checking with a lactation consultant or your pediatrician.

Adequate feeding in the first days typically means: meconium by 24 hours, transitional stools by day 3, yellow milk stool by day 5, and the number of wet diapers increasing each day (1 wet on day 1, 2 on day 2, up to 6 or more by day 6).

Track the transition

The first week of a baby's life involves a lot of diaper changes and a lot of variations in what you find. PipPoopie's diaper log makes it easy to track color changes over those first days - so if your doctor asks "when did the poop change color?" you have a real answer, not a sleep-deprived guess.