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Meconium Aspiration Syndrome

What Is Meconium Aspiration Syndrome?

Meconium is dark green fecal material that is produced in the intestines of a fetus before birth. After delivery, your newborn will pass meconium stools for the first few days of life. Stress your baby experiences before or during birth may cause your baby to pass meconium stool while still in the uterus. The meconium stool then mixes with the amniotic fluid that surrounds the fetus.

Your baby may then breathe the meconium and amniotic fluid mixture into their lungs shortly before, during, or right after birth. This is known as meconium aspiration or meconium aspiration syndrome (MAS).

Although MAS is often not life-threatening, it can cause significant health complications for your newborn. And, if MAS is severe or untreated, it can be fatal.

What Causes Meconium Aspiration Syndrome?

MAS may occur when your baby experiences stress. Stress often results when the amount of oxygen available to the fetus is reduced. Common causes of fetal stress include:

  • a pregnancy that goes past the due date (more than 40 weeks)
  • difficult or long labor
  • certain health issues experienced by the mother, including hypertension (high blood pressure) or diabetes
  • an infection

Pregnancy that lasts more than 40 weeks can result in "aging" of the placenta. The placenta is the organ that provides nourishment to the fetus in the womb. When the placenta ages, it’s not able to deliver enough oxygen to the fetus. And, the amount of amniotic fluid is decreased, which concentrates the meconium. As a result, MAS is more common in overdue newborns, compared with premature or term newborns.

What Are the Symptoms of MAS?

Respiratory distress is the most prominent symptom of MAS. Your infant may breathe rapidly or grunt during breathing. Some newborns may stop breathing if their airways are blocked by meconium. Your baby may also exhibit the following symptoms:

  • a bluish skin color, which is called cyanosis
  • limpness
  • low blood pressure

How Is Meconium Aspiration Syndrome Diagnosed?

A diagnosis is made based on your newborn’s symptoms and the presence of meconium in the amniotic fluid.

Your doctor will listen to your infant’s chest with a stethoscope to detect sounds of abnormal breathing. There are a few methods commonly used to confirm the diagnosis:

  • blood gas test to evaluate oxygen and carbon dioxide levels
  • chest X-ray to see if material has entered your newborn’s lungs
  • using a laryngoscope to look at your baby’s vocal cords to look for meconium staining

How Is Meconium Aspiration Syndrome Treated?

If MAS occurs, your newborn will need immediate treatment to remove the meconium from the upper airway. After delivery, your doctor will immediately suction the nose, mouth, and throat. Then, a tube will be placed in your newborn’s windpipe (trachea) to suction the fluid containing meconium from the windpipe. The suctioning will continue until no meconium is seen in the material removed.

If your newborn is not breathing or has a low heart rate, your doctor will use a bag and mask to help them breathe. This will deliver oxygen to your baby and help inflate their lungs. Your doctor may need to place a tube in your newborn’s windpipe to help them breathe if the infant is very ill or not breathing on their own.

After emergency treatment has been provided, your newborn may be placed in a special care unit to observe their breathing. Additional treatment may be needed to avoid complications of MAS. Five common treatments include:

  • antibiotics, such as ampicillin and gentamicin to prevent or treat an infection
  • the use of a ventilator, a breathing machine, to help your infant breathe
  • extracorporeal membrane oxygenation (ECMO) if your baby is not responding to other treatments or has high blood pressure in the lungs (for this treatment, a pump and machine that performs the function of the lungs do the work of your newborn’s heart and lungs so that these organs can heal)
  • oxygen therapy to make sure there is enough in the blood
  • the use of a radiant warmer to help your baby maintain body temperature

What Complications Are Associated with Meconium Aspiration?

Most newborns with MAS will not have any long-term health complications. However, MAS is a serious issue that can have an immediate impact on your newborn’s health. Meconium in the lungs can cause inflammation and infection.

Meconium can also block the airways, which can cause lung overexpansion. If a lung overexpands or inflates too much, it can rupture or collapse. Then air from inside the lung can accumulate in the chest cavity and around the lung. This condition, known as a pneumothorax, makes it difficult to reinflate the lung.

MAS increases the risk of your infant developing persistent pulmonary hypertension of the newborn (PPHN). High blood pressure in the vessels of the lungs restricts blood flow and makes it difficult for your baby to breathe properly. PPHN is a rare, but life-threatening condition.

On rare occasions, severe MAS may limit oxygen to the brain. This may cause permanent brain damage.

What Is the Outlook for Newborns with Meconium Aspiration?

Infants who experience mild complications of MAS usually recover well. Infants who develop brain damage or PPHN as a result of MAS may face lifelong health issues that require medical support.

How Can Meconium Aspiration Be Prevented?

Early detection is the best defense in preventing MAS. Fetal monitoring before delivery can determine whether your baby is experiencing stress. Your doctor can take steps to alleviate fetal distress during labor and reduce the potential for MAS to develop. And, if your baby is experiencing stress, your doctor will be prepared to evaluate and treat your baby right away if there are signs of MAS.

Content licensed from:

Written by: Darla Burke
Medically reviewed on: Jan 04, 2016: Laura E. Marusinec, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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