Meconium and meconium-related conditions

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Learn what meconium is and why it is important that your baby pass their meconium in the first 24 hours of life.

Key points

  • A baby should pass meconium in the first 24 hours of life.
  • If your baby does not pass meconium in the first 24 hours, speak to your doctor.


Meconium is the thick, black substance that fills the baby's intestines before birth. For the first few days, when babies pass stool, the meconium is passed out of their body. Around day three to five, a baby's bowel movements turn to yellow, seedy stools.

  • Babies should have their first meconium bowel movement within the first 24 hours of life. Some babies will pass their meconium in the delivery room. You should either observe this yourself or ask the nurse if the baby passed meconium.
  • If a baby does not have a bowel movement in the first 24 hours, a doctor needs to see the baby.
  • If a baby does not have a bowel movement in the first 24 hours, this may be due to an illness such as hypothyroidism, cystic fibrosis, blockage of the intestines or Hirschprung disease.

Meconium ileus

Meconium ileus occurs when meconium acts like a plug and blocks part of the intestine (gut) of a baby. Babies with meconium ileus:

  • do not pass meconium for the first few days
  • begin to have vomiting and enlargement of their tummy in the first few days.

About 80% to 90% of babies with meconium ileus have cystic fibrosis. Any baby who has not passed stool for the first 24 hours, or a baby who is developing vomiting and distension (enlargement) of the tummy in the first few days of life, needs to see a doctor immediately.

Meconium aspiration syndrome (MAS)

Meconium aspiration syndrome is a condition in which a baby develops problems breathing because the baby inhaled meconium into the lungs while still in the womb at the very end of the pregnancy or during the delivery. Some babies pass meconium in the womb or during delivery and do not develop MAS or any other problems. In fact, about 90% of babies born through mecium-stained amniotic fluid do not develop MAS. However, in those babies who do develop MAS, it can be mild or it can be very serious and life-threatening.

Risk factors for MAS include:

  • Post-dates babies (babies born at a gestational age of more than 41 weeks)
  • Small for gestational age babies (babies who have a low weight compared to what would be expected for their gestational age)
  • Fetal distress and/or a difficult delivery
  • Problems with the placenta or umbilical cord

Signs and symptoms of MAS

  • Difficulty breathing (fast breathing, nostrils flaring, appearance of air being sucked in between the ribs and under the ribcage and/or cyanosis, which is a blue discoloration around the lips and mouth)
  • The baby could develop an air leak (called a pneumothorax)
  • The baby could develop persistent pulmonary hypertension

If a baby has meconium aspiration syndrome, then treatment will begin right away in the delivery room. The baby may require oxygen and/or a mask over the face to deliver pressure to keep the airways open. Further treatment may include putting a tube into the airway and suctioning out some of the meconium. The baby will need to go to the special care nursery or the neonatal intensive care unit for further tests and treatment.

Meconium peritonitis

Meconium peritonitis occurs when there is rupture of the bowel before birth (the bowel opens and then there is a hole in the bowel). The meconium leaks out into the space that surrounds the bowels (peritoneum) and there is an inflammation of the lining of the abdomen (peritonitis).

Infants with cystic fibrosis are at increased risk for meconium peritonitis.

How is meconium peritonitis diagnosed?

  • It could be diagnosed before birth if the doctor sees areas of calcium deposits in the peritoneum on an ultrasound test
  • It could be diagnosed after birth if the baby is born with vomiting and an enlarged abdomen. On an X-ray, the doctor can see that the bowel is enlarged (dilated)

Why would the bowel rupture?

The bowel could rupture if there is an underlying problem, such as:

  • volvulus (twisting of the bowels)
  • small bowel atresia (abnormal formation of the bowels where the small bowel comes to an end instead of connecting to the rest of the large bowel)
  • microcolon (an abnormally narrow lower section of bowel)
  • intussusception (the bowel telescopes into itself)
  • imperforate anus (the anus is not open/patent)

What will happen?

Sometimes, the bowel heals on its own while the baby is still in the womb. Other times, the baby may require surgery to fix the underlying problem.

A fetus with meconium peritonitis needs careful monitoring, including:

  • regular ultrasounds
  • follow-up with an obstetrical team and a surgical/neonatal team at a high-level (tertiary) care centre
  • plan for delivery at a hospital that has a neonatal intensive care unit
Last updated: July 6th 2013