Meconium aspiration syndrome (MAS) is when a newborn baby breathes in a sticky substance called meconium just before or during birth. It can cause breathing problems and respiratory distress. It’s rare for MAS to cause long-term complications or health conditions. Early detection and fast treatment improve the outcomes.
Meconium aspiration syndrome (MAS or meconium aspiration) happens when a baby has breathing problems because meconium got into their lungs just before or during birth. Meconium is a sticky substance that becomes your baby’s first poop. If your baby passes meconium before birth, they may breathe it in. Inhaling meconium can block or irritate your baby’s airways, damage lung tissue and block surfactant (the substance that helps open your baby’s lungs at birth). MAS can cause respiratory problems, and in rare cases, be life-threatening.
Meconium is your baby’s first poop. It’s thick, sticky and tar-like and made up of cells, mucus, hair, bile and other materials. Babies typically pass meconium within 48 hours of birth. In some cases, babies will pass meconium during labor and delivery, putting them at risk of aspirating (or inhaling) the tacky substance.
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Meconium has a thick and sticky texture. It’s so sticky that it’s often hard to get off your baby’s bottom with a wipe. Imagine this substance in a newborn’s lungs. It can get stuck inside your baby’s airways, prevent their lungs from inflating and deprive them of air.
Meconium is passed into amniotic fluid in 12% to 20% of all births. It’s given the term meconium-stained amniotic fluid. Meconium-stained amniotic fluid is more common in full-term (40 weeks gestation) or post-term (after 42 weeks gestation) babies. Only 2% to 10% of babies born through meconium-stained amniotic fluid develop MAS.
Inhaling or breathing in meconium can be dangerous. Some of the most common signs that your baby has aspirated meconium are:
Meconium aspiration can happen for several reasons, but stress is the most common. Examples of stress could be an infection or low oxygen levels. Stress makes your baby take strong, deep gasps. This forceful gasp causes them to inhale amniotic fluid deep into their lungs. If the amniotic fluid contains meconium, the meconium gets into their lungs. The aspirated meconium fills their airways, making it hard to breathe.
Amniotic fluid that contains meconium will appear greenish-brown when the amniotic sac ruptures. Babies exposed to meconium-stained amniotic fluid may have yellow skin and nails at birth. Healthcare providers know what to look for and are trained to detect meconium aspiration.
Swallowing meconium is OK. A fetus practices swallowing by drinking amniotic fluid. So if they release small amounts of meconium and swallow it, it’s not a cause for worry. On the other hand, inhaling meconium into the lungs can be dangerous.
If healthcare providers detect meconium in your amniotic fluid, they’ll watch for signs of aspiration after your baby’s born. Just because your baby releases meconium before birth doesn’t mean they’ll breathe it in. Watching your baby closely for signs of distress is the first step in diagnosing MAS. Healthcare providers may listen to your baby’s chest and do a chest X-ray.
A chest X-ray is the most common test used to diagnose MAS. The results will show fluid in your baby’s lungs. Providers may also use blood gas tests to check oxygen and carbon dioxide levels and confirm the diagnosis.
The treatment for MAS depends on the volume and consistency of the meconium and the amount of respiratory distress your baby is experiencing. If your baby’s born crying and active, treatment is usually unnecessary.
The first treatment for MAS is suction. Healthcare providers will remove meconium from your baby’s mouth, nose and throat using a bulb syringe. They may insert a tube down your baby’s throat to remove additional meconium from their airway. If your baby still has breathing trouble, they may place a facemask with oxygen on them.
A baby with MAS may need to stay in the neonatal intensive care unit (NICU) for close monitoring and more advanced treatment. This could include:
No, you can’t prevent your baby from aspirating meconium. The best thing your healthcare providers can do is monitor your amniotic fluid for meconium and watch for fetal distress. Detecting aspiration early and quickly can prevent severe aspiration. Some risk factors for MAS include:
Long-term complications of MAS are rare. Typically, the condition is managed and treated within a few days. Newborns with MAS are at a slightly higher risk for:
Most babies who aspirate meconium don’t develop MAS. For the ones who do, only a small amount will develop health conditions. MAS is highly treatable, especially if detected early and quickly.
Most babies recover from meconium aspiration within a few hours. In serious cases, a baby may need extra time in the NICU or rely on supplemental oxygen for several days or weeks.
A note from Cleveland Clinic
Meconium aspiration syndrome is a serious but treatable condition in newborns. Your healthcare provider will check your amniotic fluid for meconium when your baby is born. If your newborn baby shows any signs of distress, your provider will remove the meconium from your baby’s nose and throat. Complications are rare when meconium aspiration is caught early and treated quickly. Most babies heal within a few days and have no long-term side effects of meconium aspiration. Remember, most babies with meconium in their amniotic fluid won’t get meconium aspiration syndrome.
Last reviewed by a Cleveland Clinic medical professional on 01/17/2023.
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