Meconium is a newborn's first poop. This sticky, thick, dark green poop is made up of cells, protein, fats, and intestinal secretions, like bile. Babies typically pass meconium (mih-KOH-nee-em) in the first few hours and days after birth. But some babies pass meconium while still in the womb during late pregnancy.
Meconium aspiration syndrome (MAS) happens when a newborn has trouble breathing because meconium got into the lungs.
Meconium can make it harder to breathe because it can:
With treatment, most babies with meconium aspiration syndrome get better with no problems.
Meconium aspiration happens when a baby is stressed and gasps while still in the womb, or soon after delivery when taking those first breaths of air. When gasping, a baby may inhale amniotic fluid and any meconium in it.
Babies are more likely to pass meconium when:
Babies who are stressed by low oxygen levels or infections also may pass meconium before birth. When meconium gets in the amniotic fluid, there's a chance a baby will breathe (aspirate) it into the lungs before, during, or after birth. But most babies with meconium in the amniotic fluid will not get MAS.
Before or at a baby's birth, doctors will notice one or more of these signs:
Doctors diagnose MAS in any baby with breathing problems who is born through meconium-stained fluid and has no other cause for the breathing problems. A chest X-ray can confirm the diagnosis. Doctors may do other tests to be sure nothing else causes the symptoms, such as a heart problem or pneumonia.
Most babies with MAS get medical care in a special care nursery or neonatal intensive care unit (NICU) and get oxygen, if needed.
A baby who gets extra oxygen but still struggles to breathe will get help from a breathing machine (ventilator). An infant with severe MAS may need more treatment, such as:
Most babies with MAS get better within a few days or weeks, depending on how much meconium they inhaled.
If a woman goes past her due date, her doctor may recommend inducing labor to help prevent MAS. If a pregnant woman's water breaks and she sees dark green stains or streaks in the fluid, she should tell her doctor right away. This is a sign that meconium is in the amniotic fluid.
In the past, doctors sometimes did amnioinfusion (using saline to dilute meconium in the amniotic fluid) or suctioned meconium out of the baby's mouth and throat at birth. But these treatments weren't found to prevent MAS, so are not routinely done.
Most infants with meconium aspiration syndrome recover completely. Some babies may have a higher risk of lung infections and wheezing, particularly in their first year of life.
Reviewed by: Jay S. Greenspan, MD
Date Reviewed: Jan 1, 2020
