Meconium aspiration syndrome (MAS) is defined as respiratory distress in the newborn due to the presence of meconium in the trachea.
Infants born through meconium-stained amniotic fluid are at risk of developing meconium aspiration syndrome, particularly in the presence of maternal and fetal risk factors. Postmaturity is a strong fetal risk factor; signs include green/yellow-colored skin; long, stained nails; and dry, scaling skin.
Soon after birth, infants present with respiratory distress (tachypnea, chest retractions, and hypoxia). Some infants may be asymptomatic and apparently vigorous at birth, and develop severe respiratory distress hours later.
Diagnosis is confirmed by chest x-ray.
Management is largely supportive. Infants should be monitored closely to ensure adequate oxygenation and ventilation.
In the presence of persistent pulmonary hypertension, inhaled nitric oxide and extracorporeal membrane oxygenation therapy may be required.
Meconium aspiration syndrome (MAS) is defined as respiratory distress in the newborn due to the presence of meconium in the trachea. It occurs exclusively in the immediate neonatal period. It also covers respiratory distress in an infant, born through meconium-stained amniotic fluid, that cannot be explained otherwise.
History and exam
Key diagnostic factors
- signs of postmaturity
- systolic murmur
- chest wall asymmetry with decreased air entry
- barrel-shaped chest
Other diagnostic factors
- chest retractions
- gestational age >42 weeks
- pregnancy-induced hypertension
- maternal diabetes mellitus
- maternal smoking or substance misuse
- fetal distress
- thick meconium
- Apgar score <7
- cesarean delivery
- black ancestry
- male sex
1st investigations to order
- blood culture
Investigations to consider
- dual pulse oximetry
- ABG (pH, PaO₂, PaCO₂)
- cranial ultrasound
vigorous infant born through meconium-stained amniotic fluid, no respiratory distress
- Transient tachypnea of the newborn
- Surfactant deficiency
- Persistent pulmonary hypertension
- Neonatal resuscitation: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care, part 5
- Management of meconium at birth
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