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Meconium Aspiration Syndrome


Arcangela Lattari Balest

, MD, University of Pittsburgh, School of Medicine

Last full review/revision Jul 2021| Content last modified Jul 2021
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 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 postmature fetus Postterm Newborn A postterm newborn is a baby delivered after 42 weeks of gestation. Near the end of a term pregnancy, the function of the placenta decreases, providing fewer nutrients and less oxygen to the... read more , it is never normal for there to be meconium noted at the delivery of a premature baby Premature Newborn A premature newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, premature newborns have underdeveloped organs, which may 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 (aspirated) in 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 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 discoloration of the skin resulting from an inadequate amount of oxygen in the blood. Cyanosis occurs when oxygen-depleted (deoxygenated) blood, which is bluish rather than... read more ) if the blood levels of oxygen are reduced. They may also develop low blood pressure Low Blood Pressure Low blood pressure is blood pressure low enough to cause symptoms such as dizziness and fainting. Very low blood pressure can cause damage to organs, a process called shock. Various drugs and... read more . The newborn's umbilical cord, nail beds, or skin may be covered in meconium, giving them a greenish yellow color.

Diagnosis of Meconium Aspiration Syndrome

  • Meconium in the amniotic fluid

  • Trouble breathing

  • Chest x-ray

Doctors base the diagnosis of meconium aspiration syndrome on the presence of meconium in the amniotic fluid at the time of birth, respiratory distress, and abnormal chest x-ray results.

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

Prognosis for Meconium Aspiration Syndrome

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. However, if the newborn's airway seems blocked by meconium, doctors try to suction it out.

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

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