Health Encyclopedia

Meconium aspiration syndrome

Definition

Meconium is the first feces (stool) of the newborn. Meconium aspiration syndrome is a serious condition in which a newborn breathes a mixture of meconium and amniotic fluid into the lungs around the time of delivery.

Alternative Names

MAS

Causes, incidence, and risk factors

Meconium aspiration syndrome is a leading cause of severe illness and death in the newborn. The possibility of inhaling meconium occurs in about 5-10% of births. It typically occurs when the fetus is stressed during labor, especially when the infant is past its due date.

Stress during labor can cause increased movement of the infant's intestines and relaxation of the anal sphincter, causing meconium to pass into the surrounding amniotic fluid. If the infant breathes while still in the uterus or while still covered by this fluid after birth, the mixture can enter the lungs and partially or completely block the infant's airways.

Risk factors include:

Fetal distress
Decreased oxygen to the infant while in the uterus
Diabetes in the pregnant mother
Difficult delivery
High blood pressure in the pregnant mother

Symptoms

Bluish skin color in the infant
Breathing problems
- Difficulty breathing (the infant needs to work hard to breathe)
- No breathing
- Rapid breathing
Dark, greenish staining or streaking of the amniotic fluid or the obvious presence of meconium in the amniotic fluid
Limpness in infant at birth
Greenish-stained skin in infant (occurs if meconium passed a long period before delivery)
Skin peeling
Weight loss

Signs and tests

Before birth, the fetal monitor may show a slow heart rate. At birth, meconium can be seen in the amniotic fluid. The infant may have a low Apgar score.

The most accurate test to check for possible meconium aspiration involves looking for meconium staining on the vocal cords. This is done in the delivery room using a device called a laryngoscope.

The health care team will listening to the infant's chest with a stethoscope and may hear abnormal breath sounds, especially coarse, crackly sounds.

A blood gas analysis shows low blood acidity, decreased oxygen, and increased carbon dioxide.

A chest x-ray may show patchy or streaky areas on lungs.

Treatment

The newborn's mouth should be suctioned as soon as the head can be seen during delivery.

Further treatment is necessary if there is thick meconium staining and fetal distress. A tube is placed in the infant's trachea and suction is applied as the endotracheal tube is withdrawn. This procedure is repeated until meconium is no longer seen in the suction contents.

The infant may be placed in the special care nursery or newborn intensive care unit. Other treatments may include:

Antibiotics to treat infection
Breathing machine to keep the lungs inflated
Use of a warmer to maintain body temperature
Tapping on the chest to loosen secretions

If there have been no signs of fetal distress during pregnancy and the baby is a vigorous full-term newborn, experts recommend against deep suctioning of the windpipe for fear of causing a certain type of pneumonia. Occasionally, a saline solution is used to wash the airway of particularly thick meconium.

Expectations (prognosis)

In most cases, the outlook is excellent and there are no bad side effects.

In more severe cases, breathing problems may occur. They generally go away in 2 to 4 days. However, rapid breathing may persist for days.

An infant with severe aspiration who requires a breathing machine may have a more guarded outcome. Lack of oxygen in the uterus or from complications of meconium aspiration may lead to brain damage. The outcome depends on the degree of brain damage.

Meconium aspiration rarely leads to permanent lung damage.

Complications

Aspiration pneumonia
Brain damage due to lack of oxygen
Breathing difficulty that lasting for several days
Collapsed lung
Persistent pulmonary hypertension of the newborn

Calling your health care provider

If the baby is born outside of the hospital and shows any signs of distress, seek immediate medical care.

Prevention

Risk factors should be identified as early as possible. If the mother's water broke at home, she should tell the health care provider whether the fluid was clear or stained with a dark substance.

Fetal monitoring is started so that any signs of fetal distress can be recognized early. Immediate intervention in the delivery room can sometimes help prevent this condition.

Review Date:10/15/2007
Reviewed By:Deirdre O’Reilly, MD, MPH, Neonatologist, Division of Newborn Medicine, Children’s Hospital Boston and Instructor in Pediatrics, Harvard Medical School, Boston, Massachusetts. Review Provided by VeriMed Healthcare Network.

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