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.
(See also Overview of General Problems in Newborns Overview of General Problems in Newborns Problems in newborns may develop Before birth while the fetus is growing During labor and delivery After birth About 9% of newborns need special care after birth due to prematurity, problems... read more .)
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 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 Preterm (Premature) Newborns A preterm newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, preterm newborns have underdeveloped organs, which may not be ready to function outside of... 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 aspirated into the lungs also causes inflammation of the lungs (pneumonitis) and increases the risk of lung infection.
Newborns with meconium aspiration syndrome are also at increased risk of persistent pulmonary hypertension of the newborn Persistent Pulmonary Hypertension of the Newborn Persistent pulmonary hypertension of the newborn is a serious disorder in which the arteries to the lungs remain narrowed (constricted) after delivery, thus limiting the amount of blood flow... read more .
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. 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.
Affected newborns 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 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 
(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 9% of newborns need special care after birth due to prematurity, problems... read more (NICU) if necessary.
If 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 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 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 or persistent pulmonary hypertension of the newborn Persistent Pulmonary Hypertension of the Newborn Persistent pulmonary hypertension of the newborn is a serious disorder in which the arteries to the lungs remain narrowed (constricted) after delivery, thus limiting the amount of blood flow... read more . 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
Most newborns with meconium aspiration syndrome have an excellent prognosis. However, occasionally, if the disorder is severe, especially if it leads to persistent pulmonary hypertension of the newborn Persistent Pulmonary Hypertension of the Newborn Persistent pulmonary hypertension of the newborn is a serious disorder in which the arteries to the lungs remain narrowed (constricted) after delivery, thus limiting the amount of blood flow... read more , it can be fatal.
Newborns with meconium aspiration syndrome may be at greater risk of asthma Asthma in Children Asthma is a recurring inflammatory lung disorder in which certain stimuli (triggers) inflame the airways and cause them to temporarily narrow, resulting in difficulty breathing. Asthma triggers... read more 
later in life.
Any problem that stressed the fetus and caused meconium passage can affect prognosis.
