Meconium aspiration syndrome is trouble breathing (respiratory distress) in a newborn who has breathed in a sterile fecal material called meconium before delivery.
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 exhaling.
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 breathing.
Most affected newborns survive, but the syndrome can be fatal if severe.
(See also Overview of General Problems in Newborns.)
Meconium is the dark green, sterile fecal material that is produced in the fetus's 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, for example, from an infection or from a low level of oxygen in the blood. Although meconium passage may be normal in a term or postterm fetus, it is not normal for a premature baby. Meconium passage in a premature baby most often means the baby developed an infection while in the womb.
Meconium aspiration syndrome occurs when a stressed fetus passes meconium in the amniotic fluid and then takes forceful gasps and breathes in (aspirates) the fluid and the meconium into the lungs.
After delivery, the aspirated meconium causes chemical irritation and inflammation (pneumonitis) of the lungs and increases the risk of lung infection.
Meconium may also 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 blocked 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).
Newborns with meconium aspiration syndrome are also at increased risk of persistent pulmonary hypertension of the newborn.
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. The chest wall may also look like a barrel if the lungs are over-expanded.
Their skin and/or lips may be bluish (a condition called cyanosis) if the blood levels of oxygen are reduced. In newborns with dark skin, the skin may appear blue, gray, or whitish, and 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.
Affected newborns may also develop low blood pressure.
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-ray.
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
If the newborn's airway seems blocked by meconium, doctors 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 (a machine that helps air get in and out of the lungs), or they may be put on continuous positive airway pressure (CPAP). CPAP allows newborns to breathe on their own while being given slightly pressurized air, with or without extra oxygen, through prongs placed in their nostrils. Newborns are admitted to the neonatal intensive care unit (NICU).
If a ventilator, CPAP, or oxygen is necessary, the lowest possible settings are used to avoid injury to the lungs. Newborns on a ventilator may be given surfactant (a substance that coats the inside of the air sacs and allows the air sacs of the lungs to remain open) and are observed closely for serious complications, such as pneumothorax or persistent pulmonary hypertension of the newborn. Newborns are taken off ventilators and oxygen as early as is safe.
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
Children who survive meconium aspiration syndrome have an increased risk of developing complications such as asthma, cerebral palsy, and developmental delay.
However, occasionally, if the disorder is severe, especially if it leads to persistent pulmonary hypertension of the newborn, it can be fatal.
