Meconium

A newborn's first stool, which is thick, dark green/black, and sticky.

What is Meconium?

Meconium is your baby's very first bowel movement. Unlike later stools, meconium is not made from breast milk or formula. Instead, it is composed of everything the baby ingested while in the womb: amniotic fluid, mucus, skin cells, and lanugo (fine hair).

What Does it Look Like?

Be prepared—it's quite different from what you might expect! Meconium is:

• Color: Very dark green or black.
• Texture: Thick, tar-like, and extremely sticky.
• Odor: Surprisingly odorless, as it doesn't contain the bacteria that cause 'stinky' diapers.

The Timeline

Most babies pass their first meconium within the first 24 to 48 hours after birth. As the baby begins to ingest colostrum and breast milk, the stool will transition to a lighter green and then to the 'mustard yellow' typical of breastfed infants.

Meconium Aspiration Syndrome (MAS)

Sometimes, a baby passes meconium before they are born, usually due to stress during labor. You'll know this has happened if your 'water breaks' and the fluid is green-tinged.

If the baby breathes in this fluid, it can cause Meconium Aspiration Syndrome, which may require them to spend some time in the NICU to have their lungs cleared and monitored.

The Bottom Line

Meconium is a sign that your baby's digestive system is 'online' and working perfectly. It's also the reason why seasoned parents recommend putting a thick layer of barrier cream (like Vaseline or diaper paste) on a newborn's bottom before the first poop—it makes cleaning up that sticky tar much, much easier!