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Meconium Aspiration Syndrome (MAS) is a form of neonatal respiratory distress caused by aspiration of meconium-stained amniotic fluid into the airways, leading to mechanical obstruction, chemical pneumonitis, and potentially air leak or persistent pulmonary hypertension (PPHN).

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https://www.youtube.com/watch?v=ZTLPOYPdw7s

Epidemiology

Occurs in term or post-term neonates
Incidence: ~5–10% of meconium-stained deliveries
More common with fetal distress (e.g., perinatal hypoxia)

Pathophysiology

Mechanism	Effect
Airway obstruction	Partial: Ball-valve effect → air trapping & hyperinflation
Complete: Atelectasis
Chemical pneumonitis	Meconium is inflammatory → alveolar damage, surfactant inactivation
Infection risk	Meconium may harbor pathogens
PPHN	Hypoxia-induced pulmonary vasoconstriction

Clinical Features

Onset at birth or shortly after. History of meconium-stained amniotic fluid. Often requires NICU admission

Signs of respiratory distress:
- Tachypnea
- Intercostal and subcostal retractions
- Grunting, nasal flaring, cyanosis

Complications

Pulmonary air-leak syndromes : Pneumothorax, pneumomediastinum
Persistent pulmonary hypertension of the newborn (PPHN)
Hypoxic ischemic injury(HII) in severe perinatal distress
Bronchopulmonary dysplasia (BPD) in prolonged cases