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Meconium Aspiration Syndrome

Medically reviewed by Last updated on Jan 5, 2023.

What is meconium aspiration syndrome?

Meconium is a baby's first bowel movement. Meconium aspiration syndrome (MAS) develops when the baby aspirates (breathes in) meconium. This usually happens while he or she is still in the womb but may happen during or shortly after birth. MAS ranges from mild to life-threatening.

What causes MAS?

Your baby may take deep breaths while he or she is still in the womb. This is a normal part of a baby's development and happens near the end of pregnancy. Your baby may gasp if he or she is not getting enough oxygen through the umbilical cord. He or she breathes in amniotic fluid when he or she takes deep breaths or gasps. If meconium is in the amniotic fluid, he or she may breathe it in along with the fluid. The meconium may block his or her airway and prevent him or her from breathing, or it may irritate his or her lungs. The following may increase your baby's risk for MAS:

  • Difficult delivery, problems with the umbilical cord, or delivery past the due date
  • Health problems in the mother, such as diabetes, high blood pressure, or gallstones
  • Cigarette smoking by the mother during pregnancy

What are the signs and symptoms of MAS?

  • Meconium or green streaks in the amniotic fluid
  • Skin that is blue from lack of oxygen, or green from being stained by meconium
  • Grunting, trouble breathing, fast breathing, or no breathing
  • Slow heartbeat
  • Limpness, or a low Apgar score (used to rate a newborn's health)

How is MAS diagnosed?

Healthcare providers may insert a scope into your baby's throat to check for meconium. His or her blood may be tested for the amount of oxygen it contains. An x-ray may be used to find signs of meconium on your baby's lungs. Healthcare providers will watch your baby for signs of MAS for the first 24 hours after he or she is born.

How is MAS treated?

Your baby may not need treatment if he or she is breathing well and his or her heartbeat is strong. He or she may need any of the following if he or she is having trouble breathing, is limp, or has a weak heartbeat:

  • Suction to remove meconium from his or her airway
  • Antibiotics to help treat a bacterial infection
  • Oxygen or certain medicines if he or she is having trouble breathing

What can I do to help prevent MAS in a future pregnancy?

Manage health conditions that can increase the risk for MAS. Tell healthcare providers if you see meconium in your water when it breaks during labor. They will monitor your baby closely during delivery.

When should I contact my baby's healthcare provider?

  • You have questions or concerns about your baby's condition or care.

When should I seek immediate care or call 911?

  • Your baby is not breathing or is having trouble breathing.
  • Your baby's skin or nails look blue.

Care Agreement

You have the right to help plan your baby's care. Learn about your baby's health condition and how it may be treated. Discuss treatment options with your baby's healthcare providers to decide what care you want for your baby. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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Further information

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