Meconium Aspiration Syndrome

Meconium is the first stool of an infant. Sometimes this stool is passed in the fluid that surrounds the baby in pregnancy. Meconium aspiration is when the meconium is inhaled into the baby’s lungs. Meconium aspiration syndrome (MAS) is a set of symptoms that may result from meconium inhalation.

  • Causes

    Not all infants that inhale meconium will develop these symptoms. It is not known why some infants develop MAS and others do not.

  • Definition

    Meconium is the first stool of an infant. Sometimes this stool is passed in the fluid that surrounds the baby in pregnancy.

    Meconium aspiration is when the meconium is inhaled into the baby’s lungs. Meconium aspiration syndrome (MAS) is a set of symptoms that may result from meconium inhalation.

  • Diagnosis

    Your doctor will ask about your symptoms and medical history and perform a physical exam. Your doctor may order tests to look for complications or causes.


    • The doctor may need to see pictures of your baby’s chest. This can be done with:

      • Chest x-ray—to look for changes caused by meconium aspiration
      • Echocardiography—to look for changes in heart function caused by meconium aspiration

    • The doctor may also need to measure the level of oxygen in the blood. This can be done with:

      • Pulse oximetry
      • Blood tests

  • Prevention

    Take these steps to help reduce your baby’s chance of MAS:

    • Manage chronic conditions. This includes high blood pressure, diabetes, respiratory disease, and heart disease.
    • If you smoke, quit.

  • Risk Factors

    Factors that increase your baby’s risk of meconium aspiration include:

    • Post-term delivery (delivery after 42 weeks of pregnancy)
    • Cesarean delivery
    • Abnormal heart rate during labor
    • Reduced amniotic fluid
    • Low or high birth weight
    • Meconium below the baby’s vocal cords
    • Low APGAR score after birth (assessment score of baby after birth)

    Factors in the mother that increase the chance of meconium aspiration in the child include:

    • High blood pressure (hypertension)
    • Diabetes
    • Respiratory disease
    • Heart disease
    • Smoking
    • Heavily meconium stained amniotic fluid
    Gestational Diabetes
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  • Symptoms

    Symptoms of MAS may include:

    • Breathing that is too rapid or too slow
    • Blue skin color due to lack of oxygen
    • Grunting
    • Nostrils that spread outward when breathing
    • Reduced muscle tone or spontaneous movement
    • A heart rate of less than 100 beats per minute

  • Treatment

    Meconium aspiration may not cause serious problems. Your doctor will monitor your baby. Other treatment may not be needed.

    If your child is not vigorous in the delivery room the doctor may need to intubate them to remove meconium from the trachea (breathing tube).

    Supportive care may be needed if the aspiration is causing breathing difficulty. Your baby may need to be monitored in a neonatal intensive care unit (NICU).

    Talk with your doctor about the best treatment plan. Options include: