What are the key clinical signs of Meconium Aspiration Syndrome in a newborn presenting with respiratory distress?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 22 August 2025Updated: 22 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

Key clinical signs of Meconium Aspiration Syndrome (MAS) in a newborn presenting with respiratory distress include:

  • Respiratory distress manifesting as tachypnoea, grunting, nasal flaring, and chest retractions, indicating increased work of breathing .
  • Cyanosis due to impaired oxygenation from airway obstruction and inflammation caused by meconium in the airways .
  • Coarse crackles and rhonchi on auscultation, reflecting airway obstruction and inflammation .
  • Barrel-shaped chest or hyperinflation may be observed due to air trapping from partial airway obstruction .
  • Signs of hypoxia such as lethargy or poor feeding may be present secondary to respiratory compromise .
  • In severe cases, signs of pulmonary hypertension and cardiovascular instability may develop, including hypotension and poor peripheral perfusion .

These clinical features arise from the pathophysiology of MAS, where aspirated meconium causes airway obstruction, chemical pneumonitis, surfactant dysfunction, and pulmonary vasoconstriction, leading to respiratory distress shortly after birth .

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