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Meconium Aspiration Syndrome

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Overview

Meconium aspiration syndrome (MAS) describes a spectrum of disorders due to the inhalation of meconium. During labour or delivery, a neonate may pass meconium, resulting in meconium-stained amniotic fluid, which may be aspirated and can result in MAS and respiratory distress.

Pathophysiology

The exact pathophysiology of MAS is not completely understood, however, it is thought to be due to meconium passage, aspiration and obstruction of the airway, airway inflammation, and surfactant inactivation.

Epidemiology

  • MAS is more common in post-term babies and up to 52% of reports have been made in babies born after 42 weeks gestation

Risk Factors

Certain risk factors can increase the risk of passing meconium in utero:

  • Maternal hypertension and pre-eclampsia
  • Oligohydramnios
  • Maternal smoking
  • Maternal cocaine use

Presentation

MAS is diagnosed in the presence of meconium-stained amniotic fluid and respiratory distress that cannot be explained by another condition. Features of respiratory distress include:

  • Tachypnoea
  • Grunting
  • Chest recessions
  • Nasal flaring
  • Cyanosis

Features of post-maturity may be present:

  • Vernix – a white, waxy substance covering the neonate
  • Peeling skin
  • Long fingernails

Investigations

Overview

Management

Overview

Infants with MAS and respiratory distress are treated in the neonatal intensive care unit with close monitoring. Supportive treatment is given including oxygenation, blood pressure control, correcting acidosis, hypoglycaemia, and other metabolic complications that arise.

Complications

Prognosis

  • Mild respiratory distress usually subsides within 4 days and most infants recover

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