Meconium Aspiration Syndrome (MAS)

Perinatal death, especially one that is sudden, is an emotionally traumatic experience for everyone involved and should not be taken lightly. The perinatal period is defined as the period that commences after 22 completed weeks of gestation, which ends seven completed days after birth. Perinatal death is also known as stillbirth, and globally, more than 2 million stillbirths occur each year 12. One cause of perinatal death is meconium aspiration syndrome (MAS). Meconium, known colloquially as ‘the first stool of the newborn’, is a viscous, dark-green substance consisting of intestinal epithelial cells, lanugo, mucous, and intestinal secretions. 85
95% of meconium is liquid, formed by water. The remaining percentage constitute solid components, the

It is secreted by type II alveolar cells, which secrete alveolar fluid (surfactant is a component of alveolar fluid). Surfactant is a mixture of phospholipids and lipoproteins, which serves to lower the surface tension of alveolar fluid,
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preventing collapse of alveoli and maintaining their patency 8. Meconium, when aspirated into the lungs, deactivates surfactant. Research has also shown that meconium disturbs surfactant synthesis, with a study concluding that surfactant phosphatidylcholine (a phospholipoprotein which forms about 85% of the lipid component in surfactant) concentrations are low in infants with meconium aspiration syndrome 14. In addition, another study has demonstrated the surfactant-stripping effect of meconium, due to the high minimum surface tensions of the major free fatty acids of meconium (palmitic, stearic, and oleic acids) 15,16. These effects can cause negatively impact pulmonary function, one of which is diffuse atelectasis 13. Figure 5-2: Chest radiograph of a full-term infant with coarse interstitial infiltrates of meconium aspiration pneumonitis. Retrieved from: