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Meconium Aspiration Syndrome

Meconium Aspiration Syndrome


Meconium aspiration syndrome, or MAS, occurs when a newborn inhales meconium into its respiratory system. Meconium is a thick, sticky substance found in the intestines of a fetus or newborn.

What is going on in the body?

Meconium may be released into the amniotic fluid when a fetus is in distress. This may occur when a fetus is not getting enough oxygen or nutrients. If this happens, the amniotic fluid surrounding the fetus goes from clear to green. As a newborn takes his or her first breath, or aspiration, the meconium can be inhaled into the lungs. It may partly or completely block the airways. This keeps the baby from getting enough oxygen.
In developed countries, 8% to 20% of the babies born after 34 weeks gestation have meconium-stained amniotic fluid. As many as 1% to 9% of these babies develop meconium aspiration syndrome. MAS is a leading cause of serious illness and death among newborns.


What are the causes and risks of the condition?

Following are some of the factors that increase the risk of meconium aspiration syndrome:
  • fetal distress during labor
  • high blood pressure in the mother during her pregnancy
  • low levels of amniotic fluid in the uterus
  • placental insufficiency, which is the failure of the placenta to supply nutrients to the fetus
  • preeclampsia, a complication marked by swelling and high blood pressure
  • pregnancy that lasts 42 weeks or longer
  • smoking during pregnancy
  • use of drugs, such as cocaine, during pregnancy
  • infection in the fetus


What can be done to prevent the condition?

Meconium aspiration is not always preventable. The following steps may help in some situations:
  • If at all possible, a baby should be delivered before the pregnancy reaches 42 weeks.
  • Babies at high risk for MAS should be monitored closely after birth. This includes postmature babies, and those who were in fetal distress during labor.
  • If a woman's water breaks at home, she should tell her healthcare provider the color of the fluid.
  • When green-tinged amniotic fluid is reported or seen, labor should be monitored closely.
  • At birth, the healthcare provider should suction out as much meconium as possible from the mouth, nose, and airways.


How is the condition diagnosed?

Fetal monitoring during labor may help detect babies at risk for MAS. At birth, the baby with MAS may have low APGAR scores. The healthcare provider may order arterial blood gases, which detect breathing problems. A chest X-ray may show white patches in the lung fields if the infant has aspirated meconium.

Long Term Effects

What are the long-term effects of the condition?

Up to 20% of the babies with meconium aspiration syndrome die from respiratory problems. Other possible complications include the following:
  • atelectasis, which is a collapsed lung
  • chronic lung problems
  • permanent brain damage
  • pneumonia
  • seizures


What are the treatments for the condition?

Treatment for MAS may include the following:
  • antibiotics, if an infection is suspected
  • extracorporeal membrane oxygenation, which uses a special machine to add oxygen to the baby's blood and circulate it
  • inhaled nitric oxide
  • medications to increase blood flow to the lungs
  • oxygen therapy
  • suctioning meconium from the baby's airway
  • use of a ventilator, or artificial breathing machine

Side Effects

What are the side effects of the treatments?

Use of a ventilator and other inhalation treatments may cause lung damage. Medications used to treat MAS may cause rash, upset stomach, or allergic reactions.

After Treatment

What happens after treatment for the condition?

If pneumonia develops, the baby may need antibiotics for several weeks. Some infants recover completely from MAS. Others may have permanent damage to the lung, brain, or kidneys.


How is the condition monitored?

Any new or worsening symptoms should be reported to the healthcare provider.

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