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Meconium Aspiration Syndrome

  • Cynthia M. Johnson, MA
Publication Type:


Meconium Aspiration Syndrome


Meconium aspiration syndrome (MAS) is a set of symptoms that happen when an infant inhales meconium. Meconium is an infant's first stool. Sometimes it is passed into the fluid that surrounds the baby in the womb.


Not all infants who inhale meconium will have MAS. It is not known why some infants get MAS and others do not.

Risk Factors

Things that may raise a baby’s risk of inhaling meconium are:

  • Being born after 42 weeks
  • Cesarean section delivery
  • Abnormal heart rate during labor
  • Low levels of amniotic fluid
  • Low or high birth weight
  • Meconium below the baby’s vocal cords

Things in a mother that may raise the chance of meconium aspiration in the baby are:

Gestational Diabetes.

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MAS may cause:

  • Breathing that is too fast or too slow
  • Blue skin color
  • Grunting
  • Nostrils that spread out when breathing
  • Low muscle tone or muscle spasms


This problem is diagnosed in a newborn based on symptoms and signs of meconium in the fluid. The diagnosis can be confirmed with a chest x-ray. Blood tests will also be done.


The goal of treatment is to help with breathing. This can be done with:

  • Intubation to open the airway and suction it as needed
  • Oxygen therapy to ease breathing
  • Breathing support in babies who cannot breathe on their own


There are no methods to prevent MAS.





  • Chettri S, Bhat BV, et al. Current concepts in the management of meconium aspiration syndrome. Indian Journal of Pediatrics, 2016; 83 (10): 1125-1130.
  • Meconium aspiration. Nemours Kids Health website. Available at: http://kidshealth.org/parent/medical/lungs/meconium.html.
  • Meconium aspiration syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/meconium-aspiration-syndrome.


  • Rimas Lukas, MD
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.