“Meconium” is the medical term for the substance (stool) that is passed during a baby’s first bowel movement. You’ll typically see it within the first 2 days after birth, but it may happen sooner or later or even over several bowel movements.

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Newborns experience a lot of firsts in their early days. One you may not anticipate with much enthusiasm is their first bowel movement, when they pass a substance called meconium. Though meconium may look concerning, it is harmless if a baby passes it soon after birth.

Here’s what you need to know about meconium, what it looks like, and what it means if your baby passes it sooner or later than what is considered typical.

Meconium is a baby’s first bowel movement, aka poop. It is unlike other stools, though. This is because it is sticky and thick, and it ranges in color from green to brown to black.

Meconium is entirely typical and expected. The substance contains what was inside the baby’s intestines when they were still in the womb. It’s made up of cellular debris from the fetus like skin, hair, and other secretions.

During pregnancy, a baby practices breathing by swallowing amniotic fluid. Some of the waste is passed through their urination back into the amniotic fluid. The other waste products remain in the baby’s intestines until birth.

Passing meconium after birth indicates that your baby’s intestines are working properly.

Most babies will pass meconium within the first 48 hours after birth, then go on to have more typical-looking bowel movements. Your doctor will likely tell you to look out for this substance when you are changing diapers.

Between 12% and 20% of babies pass their meconium during the birthing process, according to experts. When this happens, your doctor will notice a change in the color of the amniotic fluid.

Up to 40% of babies who are born after their due dates (sometimes referred to as “late-term“) may pass their meconium while still in the womb, experts say.

For some babies, passing meconium early may just be part of the natural maturation of the gastrointestinal tract. For others, it may be due to:

Some babies who pass meconium into the amniotic fluid before birth may breathe in (aspirate) the meconium. Doing so may lead to meconium aspiration syndrome (MAS). This condition causes inflammation, breathing issues, or even a lung infection (pneumonia).

MAS is more common in late-term babies. That said, only 2–10% of babies who pass meconium into the amniotic fluid experience MAS.

Treatment depends on a baby’s symptoms and may include:

You cannot necessarily prevent meconium aspiration.

This condition can only happen if a baby has passed meconium into the amniotic fluid. So identifying the aspiration early is key, suggest. This can lead to early treatment and a better outcome.

Some causes of MAS may be linked to drug use by the birthing parent, perinatal infections, and other health conditions of the birthing parent. Keeping up with routine prenatal appointments may help identify these situations before they put stress on the fetus.

Meconium staining, or meconium-stained amniotic fluid, is relatively common and refers to the color of amniotic fluid during birth. Amniotic fluid is typically clear or straw-colored. When it is stained with meconium, it may appear brown or green.

Stained amniotic fluid is a sign to the medical team that a resuscitation team should be at the ready during delivery to assess whether a baby has aspirated meconium.

Yes, it’s rare but possible for a newborn not to pass meconium. If a baby does not pass meconium within 2 days after birth, a doctor may examine them for health issues, like:

Other factors that may delay meconium include:

It’s important to let your healthcare professional know if and when you observe that your baby has passed the meconium because it indicates your child’s intestines are working properly.

When it happens, you change the meconium diaper as you would any other poopy diaper. Use your preferred disposable or cloth wipes to cleanse the area (wiping front to back) before putting on a fresh disposable or cloth diaper.

What happens when a baby is born with meconium?

If a baby’s amniotic fluid is stained with meconium, it may lead to MAS in up to 10% of babies. Additional medical care may be needed to address breathing issues or infection.

What happens if a baby swallows meconium?

Swallowing meconium is not the same as breathing it in, or aspirating it. Swallowing meconium doesn’t necessarily lead to health issues — only if the baby aspirates in the meconium while swallowing it.

What causes a baby to have meconium in the womb?

A baby may pass meconium in the amniotic fluid as part of the natural maturation of the digestive system. Other reasons include low oxygen levels, placenta issues, low amniotic fluid, infection, and drug use by the birthing parent.

Seeing meconium in the 1 or 2 days after birth is considered typical, say. In fact, that first meconium diaper is a rite of passage of sorts.

Passing meconium into the amniotic fluid before birth may put a baby at risk for MAS. Passing it later than 48 hours after birth may be a sign of an intestinal blockage or other health issues, according to experts.

If you have concerns about your pregnancy or your baby’s health, make an appointment with your doctor. The good news is that most babies with MAS make a full recovery.