Meconium is a baby’s first poop. This black, tar-like substance is made up of cells, proteins, fats, and intestinal secretions. Meconium is sterile and has no smell.

Babies usually pass meconium in their first few hours or days of life. As a baby starts feedings of breast milk or formula, their poop will change from black to dark green to yellow. 

Most babies pass meconium after birth, but some pass their first poop while still in the uterus. This causes the amniotic fluid surrounding them to become contaminated with meconium and can lead to serious health problems if the baby takes that fluid into the lungs.

This article provides everything you need to know about meconium.

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Meconium: What Is Baby’s First Poop?

Meconium is a thick, sticky substance made up of cells, protein, fats, and intestinal secretions like bile. It is usually black or dark green. Meconium has no smell because the baby’s digestive tract has no bacteria yet. Once the baby starts drinking breast milk or formula, their gut will be colonized with bacteria, which gives stool its odor. 

It is common for a baby’s poop to change color and consistency during the first few days of life. However, poop that is white or red is never normal. If your baby’s poop is white or clay-colored, see a healthcare provider; this could be a sign of liver disease. Reddish poop could indicate bleeding in the digestive tract. 

How Long Before Meconium Transitions to Normal Poop?

Meconium typically changes to normal poop within a few days. Once a baby starts eating after birth, their poop quickly changes. Breastfed babies usually have poop that looks like Dijon mustard. It is yellow, seedy, and a little watery. Formula-fed babies have poop that looks like yellow or tan paste; it is less watery.

When Meconium Is Dangerous

Meconium is normal but can become dangerous when a baby inhales it. This can occur when a baby passes meconium in the womb or during childbirth, known as meconium aspiration syndrome.

Meconium aspiration syndrome refers to breathing problems when a baby breathes in (aspirates) meconium. This can happen when a baby is under stress during labor and delivery. They may gasp in the womb or after delivery and breathe in amniotic fluid. A baby may be under stress during birth due to a lack of blood or oxygen, such as a problem with the placenta or umbilical cord.

When a baby breathes in amniotic fluid stained with meconium, their breathing may be affected. Meconium can clog a baby’s airways, making it difficult to breathe. It can also irritate the airways and cause injury to the lung tissue. Meconium may block surfactant, a fatty substance that helps a baby breathe after birth.

Most babies who pass meconium in the amniotic fluid do not breathe it in. And those who do aspirate meconium usually get better with no long-term issues. 

When a baby’s meconium is extremely thick and sticky, it can cause a blockage in the intestine known as meconium ileus. This usually occurs in babies with cystic fibrosis.

Confirming Meconium Aspiration Syndrome

A baby is usually diagnosed with meconium aspiration syndrome when experiencing breathing problems, and meconium has been found in the amniotic fluid. 

Meconium aspiration can lead to the following symptoms in a newborn:

  • Skin that appears blue (cyanosis)
  • Breathing problems 
  • Limp muscles at birth 
  • Slow heart rate 

A healthcare provider may use the following diagnostic tools to determine if your baby has aspirated meconium:

  • Physical exam: The healthcare provider will listen to the infant’s chest with a stethoscope to detect crackly breath sounds. This may be done by a pediatric nurse or a neonatologist (a medical doctor specializing in treating newborns). 
  • Blood gas analysis: Your provider may recommend a blood test to check for a low (acidic) blood pH, decreased blood oxygen, and increased blood carbon dioxide.
  • Chest X-ray: If your provider orders a chest X-ray, you might see patchy or streaky areas in the lungs that appear white. 

If your healthcare provider suspects meconium aspiration syndrome during labor and delivery, they will likely call in a special care team to be present at the birth. This team of a neonatologist and neonatology nurses may come from the nursery or the neonatal intensive care unit (NICU). 

Meconium is present in the amniotic fluid in about 10% of normal pregnancies. If the baby is active and crying, there is no need for medical intervention. 

The risk of meconium aspiration syndrome increases when a baby is under stress in the womb. This stress can cause the baby to pass meconium into the amniotic fluid. Risk factors for fetal stress include:

  • Post-term pregnancy (lasting longer than 42 weeks)
  • Decreased oxygen supply to the baby
  • Gestational diabetes 
  • Prolonged or difficult labor
  • Infection in the placenta 
  • High blood pressure in the birthing parent
  • Drug use during pregnancy 

How Do Providers Treat Inhaled Meconium?

When a baby is born with meconium aspiration syndrome, treatment is needed immediately. The exact treatment options depend on the baby's symptoms and overall health. When infants have trouble breathing, they are immediately transported to the hospital's nursery or NICU. 

Treatment and prevention of meconium aspiration syndrome is suctioning the mouth and nose of the baby as soon as they are born, typically before they cry or take their first breath. Other treatment options include:

  • Oxygen 
  • Antibiotics
  • Breathing machine (ventilator) 
  • Intravenous (IV) nutrition
  • Radiant warmer 

In severe cases, the newborn may need: 

In the past, babies with meconium aspiration syndrome were always given a breathing tube (intubation) so that the medical team could suction any fluid out of their airways. This is no longer standard practice and is not necessary unless the baby is not breathing. The healthcare provider may use a bulb syringe to gently remove excess fluid from the baby's nose and mouth. 


Since the risk of meconium aspiration syndrome increases when a pregnant person is past their due date, inducing labor may lower the risk. A healthcare provider will likely call in a neonatology team if there are signs of fetal distress during labor and delivery. Tell your healthcare team immediately if your water breaks and the liquid appears brown or green. 

Newborn Meconium Aspiration Syndrome Recovery

The recovery process for meconium aspiration syndrome depends on how severe the baby’s symptoms are and how long they last. About 5% of babies with meconium in their amniotic fluid develop meconium aspiration syndrome. Most babies with this condition do not develop long-term complications.

Although rare, a baby inhaling meconium may have coughing and wheezing problems that last for years. It is possible to develop persistent pulmonary hypertension of the newborn (PPHN), a disorder characterized by problems with the blood flow to and from the lungs. This is a very rare complication. 


Meconium, a baby’s first poop, is black and sticky. It contains cells, proteins, fats, and intestinal secretions. Babies usually pass meconium in the first hours or days of life. If a baby passes meconium in the womb, they are at risk of breathing it in. Meconium aspiration syndrome occurs when a baby aspirates amniotic fluid containing meconium and has breathing problems.

By Carrie Madormo, RN, MPH

Carrie Madormo, RN, MPH, is a health writer with over a decade of experience working as a registered nurse. She has practiced in a variety of settings including pediatrics, oncology, chronic pain, and public health.

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