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Meconium aspiration syndrome


Meconium aspiration syndrome occurs when a newborn baby breathes a mixture of meconium and amniotic fluid into the lungs around the time of delivery. It is a serious condition.

Alternative Names

MAS; Meconium pneumonitis (inflammation of the lungs)


Meconium is the early feces (stool) passed by a newborn soon after birth. It is passed from the body before the baby has started to digest breast milk (or formula).

In some cases, the baby passes meconium while still inside the uterus. This will happen when babies are "under stress" because the supply of blood and oxygen decreases. This is often due to problems with the placenta.

Once the meconium has passed into the surrounding amniotic fluid, the baby may breathe meconium into the lungs. This may happen while the baby is still in the uterus, or still covered by amniotic fluid after birth. The meconium can also block the infant's airways right after birth.

This condition is called meconium aspiration. It can cause breathing problems due to swelling (inflammation) in the baby's lungs after birth.

Risk factors that may cause stress on the baby before birth include:

  • "Aging" of the placenta if the pregnancy goes far past the due date
  • Decreased oxygen to the infant while in the uterus
  • Diabetes in the pregnant mother
  • Difficult delivery or long labor
  • High blood pressure in the pregnant mother


  • Bluish skin color (cyanosis) in the infant
  • Difficulty breathing (the infant needs to work hard to breathe)
  • No breathing or rapid breathing
  • Limpness in infant at birth

Exams and Tests

Before birth, the fetal monitor may show a slow heart rate. During delivery or at birth, meconium can be seen in the amniotic fluid and on the infant.

The infant may need help with breathing or heartbeat right after birth, and may have a low Apgar score.

The health care team will listen to the infant's chest with a stethoscope and may hear abnormal breath sounds, especially coarse, crackly sounds.

A blood gas analysis will show low (acidic) blood pH, decreased oxygen, and increased carbon dioxide.

A chest x-ray may show patchy or streaky areas in the infant's lungs.


A special care team should be present when the baby is born if traces of meconium are found in the amniotic fluid. If the baby is active and crying, no treatment is needed.

If the baby is not active and crying right after delivery, a tube is placed in the infant's airway by a nurse or doctor. Suction is used to remove any meconium. This procedure may be repeated more than once.

If the baby is not breathing or has a low heart rate, the team will help the baby breathe using a face mask attached to a bag that delivers an oxygen mixture to inflate the baby's lungs.

The infant may be placed in the special care nursery or newborn intensive care unit in order to be watched closely. Other treatments may include:

  • Antibiotics to treat infection
  • Breathing machine (ventilator) to keep the baby's lungs inflated
  • Oxygen to keep blood levels normal
  • Radiant warmer to maintain body temperature

Outlook (Prognosis)

In most cases, the outlook is excellent and there are no long-term health effects.

  • Breathing problems may be more severe in some cases. These will often go away in 2 to 4 days. However, rapid breathing may continue for several days.
  • Although not common, your infant may need a breathing machine. Many problems can develop while the child is using a breathing machine.
  • Meconium aspiration rarely leads to permanent lung damage.

At times, meconium may be present at birth because there is a severe problem with your baby.

A serious problem with the blood circulation to and from the lungs may occur. This is called persistent pulmonary hypertension of the newborn (PPHN). As a result, the baby may not be able to get enough blood into the lungs and out to the rest of the body.


Staying healthy during pregnancy and following your health care provider's advice can often prevent problems that lead to meconium being present.

Your healthcare providers will want to be prepared for meconium being present at birth if:

  • Your water broke at home and the fluid was clear or stained with a greenish or brown substance.
  • Any testing done during your pregnancy during indicates there may be problems present.
  • Fetal monitoring shows any signs of fetal distress can be found early.


Abu-Shaweesh JM. Respiratory disorders in preterm and term infants. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 9th ed. St. Louis, Mo: Mosby Elsevier; 2010:chap 44.

Singh BS, Clark RH, Powers RJ, Spitzer AR. Meconium aspiration syndrome remains a significant problem in the NICU: outcomes and treatment patterns in term neonates admitted for intensive care during a ten-year period. J Perinatol. 2009;29:497-503.

Kattwinkel J, Perlman JM, et al. Part 15: neonatal resuscitation: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122:S909-S919.