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Extracted from Myles Textbook for Midwives 15th Edition. Diane M. Fraser, Margaret A. Cooper (Eds). London; Churchill Livingstone: 2009. Courtesy Elsevier.

Meconium is the stool of the fetus, formed before birth and composed of materials ingested in the uterus, including intestinal epithelial cells, lanugo, mucus, amniotic fluid, bile and water. Unlike later faeces it is viscous, sticky and tar-like, and is usually very dark green in colour. The presence of meconium in amniotic fluid in the second stage of labour is an indication of potential fetal compromise and experienced obstetric advice must be sought. Most babies born through meconium stained liquor have not inhaled any particulate matter into the lower respiratory tract. However, if thick meconium is present and obstructing the airway, suction under direct vision should be performed. Meconium may also need to be aspirated from the trachea.

Meconium aspiration syndrome

A baby can develop meconium aspiration syndrome if stimulated to breathe or gasp before or after birth if there is meconium in the airway that could be inhaled.

  • The initial respiratory distress may be mild, moderate or severe, with a gradual deterioration over the first 12 - 24 hours in moderate or severe cases
  • The meconium becomes trapped in the airway and causes a ball-valve effect: air can be inhaled is trapped behind the meconium blockage and cannot be exhaled
  • The accumulation of air can lead to rupture of the alveoli and cause the development of a pneumothorax
  • Where meconium is in contact with lung tissue, pneumonia may occur
  • Surfactant is broken down in the presence of meconium

These factors combine with a previously hypoxic infant to produce a severe disease process. These babies will need full intensive care and ventilation to prevent further deterioration.

The Practising Midwife featured articles

Cochrane Corner: Antibiotics for meconium-stained amniotic fluid in labour for preventing maternal and neonatal infections 2015; 18(2): 35 - 37 Author: Valerie Smith

Facilitating normal physiology in the presence of meconium stained liquor 2015; 18(6): 16 - 19 Author: Julika Hudson

Further reading

MedlinePlus (2013). Meconium aspiration syndrome. Available at:

Vidyasagar, Bhat. Pathophysiology of meconium aspiration syndrome. BMJ Best Practice. Available at:


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