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Meconium Aspiration Syndrome


Arcangela Lattari Balest

, MD, University of Pittsburgh, School of Medicine

Reviewed/Revised Jul 2023 | Modified Sep 2023
Topic Resources

Meconium aspiration syndrome is trouble breathing (respiratory distress) in a newborn who has breathed (aspirated) a dark green, sterile fecal material called meconium into the lungs before or around the time of birth.

  • Even though fetuses do not eat, their intestines contain a sterile substance called meconium.

  • Fetuses sometimes pass meconium into the amniotic fluid before birth, either normally or in response to stress, such as a lack of oxygen.

  • Stress may cause fetuses to gasp reflexively, thus inhaling amniotic fluid containing meconium into their lungs.

  • Affected newborns have bluish or gray skin and/or lips, rapid and labored breathing, and can make a grunting sound when breathing out.

  • The diagnosis is based on seeing meconium in the amniotic fluid at birth, along with trouble breathing and abnormal chest x-ray results.

  • Affected newborns require supplemental oxygen and may require assistance with a ventilator.

  • Most affected newborns survive, but the syndrome can be fatal if severe.

Meconium is the dark green, sterile fecal material that is produced in the intestine before birth. Meconium is usually passed after birth when newborns start to feed, but sometimes it is passed into the amniotic fluid before or around the time of birth. Passage of meconium may be normal before birth, particularly just before or after the due date. But sometimes meconium passage occurs in response to stress, such as by an infection or by an inadequate level of oxygen in the blood. Although meconium passage may be normal in a term or postterm fetus Postterm Newborns A postterm newborn is a baby delivered at or after 42 weeks of gestation. Near the end of a term pregnancy, the function of the placenta decreases, providing fewer nutrients and less oxygen... read more , it is never normal for there to be meconium noted at the delivery of a premature baby Preterm (Premature) Newborns A preterm newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, preterm newborns may have underdeveloped organs that are not be ready to function outside... read more . Meconium passage in a premature baby most often means the baby developed an infection while in the womb.

Meconium aspiration syndrome occurs when stress (such as infection or low oxygen levels) causes the fetus to take forceful gasps, so that the amniotic fluid containing meconium is breathed in (aspirated) and deposited into the lungs. After delivery, the aspirated meconium may block the newborn's airways and cause regions of the lungs to collapse. Sometimes airways are only partially blocked, allowing air to reach the parts of the lung beyond the blockage but preventing it from being breathed out. Thus, the involved lung may become over-expanded. When a portion of the lung continues to over-expand, it can rupture and then collapse the lung. Air may then accumulate within the chest cavity around the lung (pneumothorax Pneumothorax in the Newborn Pneumothorax is a collection of air between the lung and the chest wall that develops when air leaks out of the lung. This disorder may develop in newborns who have lung disorders such as respiratory... read more ).

Meconium Aspiration Syndrome (MAS)

Meconium aspirated into the lungs also causes inflammation of the lungs (pneumonitis) and increases the risk of lung infection.

Symptoms of Meconium Aspiration Syndrome

Affected newborns have respiratory distress, in which they breathe rapidly, draw in their lower chest wall while breathing in, and grunt during breathing out.

Their skin and/or lips may be bluish (a condition called cyanosis Cyanosis Cyanosis is a bluish or grayish discoloration of the skin resulting from an inadequate amount of oxygen in the blood. Cyanosis occurs when oxygen-depleted (deoxygenated) blood, which is bluish... read more ) if the blood levels of oxygen are reduced. In newborns of color, the skin may change to colors such as yellow-gray, gray, or white. These changes may be more easily seen in the mucous membranes lining the inside of the mouth, nose, and eyelids.

The newborn's umbilical cord, nail beds, or skin may be stained by meconium, giving them a greenish yellow color.

Diagnosis of Meconium Aspiration Syndrome

  • Meconium in the amniotic fluid

  • Trouble breathing

  • Chest x-ray

Doctors suspect meconium aspiration syndrome if a newborn has trouble breathing and meconium is seen in the amniotic fluid and on the newborn at the time of birth.

Doctors confirm the diagnosis by doing a chest x-rays.

Cultures of blood may be done to look for certain kinds of bacteria.

Treatment of Meconium Aspiration Syndrome

  • Sometimes suctioning of the airways

  • Measures to support breathing

  • Sometimes surfactant and antibiotics

  • Treatment of any underlying disorder

Doctors always used to do suctioning whenever they saw meconium in the amniotic fluid or in the newborn's mouth, but this has not been shown to help and may cause complications. However, if the newborn's airway seems blocked by meconium, doctors do try to suction it out.

Newborns who have trouble breathing after delivery may need to have a breathing tube placed in their windpipe and be placed on a ventilator Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more (a machine that helps air get in and out of the lungs), or they may be put on continuous positive airway pressure Obstructive sleep apnea Obstructive sleep apnea (CPAP). CPAP allows newborns to breathe on their own while being given slightly pressurized air, with or without extra oxygen, through prongs placed in the nostrils. Newborns are admitted to the neonatal intensive care unit Neonatal intensive care unit (NICU) Problems in newborns may develop Before birth while the fetus is growing During labor and delivery After birth About 10% of newborns need some special care after birth due to prematurity, problems... read more (NICU) if necessary.

Newborns may be treated with antibiotics given by vein if a bacterial infection is thought to be what stressed the fetus before birth.

Prognosis for Meconium Aspiration Syndrome

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