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[Conditions](https://durgical.com/en/conditions/) · [Pediatrics and neonatology](https://durgical.com/en/conditions/)

# Meconium aspiration syndrome

Breathing problems in a newborn who inhaled meconium (the first stool) in the womb or at birth. It can be mild or life-threatening.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/)
- [Segmental bronchi](https://durgical.com/en/anatomy/segmental-bronchus/)
- [Lobar bronchi](https://durgical.com/en/anatomy/lobar-bronchus/)
- [Trachea](https://durgical.com/en/anatomy/trachea/)
- [Pleura](https://durgical.com/en/anatomy/pleura/)

## Why it happens

- [Neonatal respiratory distress syndrome: surfactant and hyaline membranes](https://durgical.com/en/general-pathology/neonatal-respiratory-distress-syndrome-surfactant-and-hyaline-membranes/)
- [Surface tension, surfactant and Laplace's law](https://durgical.com/en/physiology/surface-tension-surfactant-and-laplace-s-law/)
- [Fetal circulation and the transition at birth](https://durgical.com/en/physiology/fetal-circulation-and-the-transition-at-birth/)
- [The pulmonary circulation and hypoxic vasoconstriction](https://durgical.com/en/physiology/the-pulmonary-circulation-and-hypoxic-vasoconstriction/)

## What it is

Respiratory distress in a newborn born through meconium-stained amniotic fluid, with compatible chest X-ray findings, that cannot be explained otherwise. Meconium in the airways causes obstruction, chemical pneumonitis and surfactant inactivation.

## Who gets it

Mostly seen in term and post-term babies. Meconium-stained fluid is present in a sizeable minority of births, but only a small fraction of these babies develop the syndrome. It remains an important cause of severe neonatal respiratory failure in Latin American units where post-term births and limited perinatal monitoring persist.

## Causes

- Fetal stress or hypoxia that triggers passage of meconium into the amniotic fluid
- Fetal gasping in utero or first breaths at birth that draw meconium into the airways

## Risk factors

- Post-term pregnancy (over 41 to 42 weeks)
- Fetal distress, abnormal fetal heart rate tracing or placental insufficiency
- Preeclampsia, maternal hypertension or diabetes
- Intrauterine growth restriction and oligohydramnios
- Thick («pea soup») meconium

## Pathophysiology

Meconium plugs airways completely (atelectasis) or partially, creating a ball-valve effect with air trapping and a risk of air leak. It inactivates surfactant and causes a chemical inflammatory pneumonitis. Hypoxia and acidosis keep pulmonary vascular resistance high, so persistent pulmonary hypertension with right-to-left shunting often follows.

## Classification

- Mild: low oxygen need, short course
- Moderate: oxygen need above about 40% or CPAP
- Severe: requires mechanical ventilation, often with pulmonary hypertension

## Symptoms and signs

- Meconium staining of the [skin](https://durgical.com/en/anatomy/skin/), nails or umbilical cord
- Respiratory distress at birth: tachypnoea, grunting, retractions and cyanosis
- Barrel-shaped chest from air trapping
- Depressed baby (limp, poor respiratory effort) when born after asphyxia
- Crackles on auscultation

## Red flags

- Hypoxaemia out of proportion to the X-ray or a pre- and post-ductal saturation difference (persistent pulmonary hypertension)
- Sudden deterioration, asymmetric breath sounds or shift of the heart sounds (pneumothorax)
- Hypotension or poor perfusion
- Seizures or abnormal tone (hypoxic-ischaemic encephalopathy)

## Diagnosis

**Clinical**
History of meconium-stained amniotic fluid plus respiratory distress from birth, with no better explanation.

**Tests**
Arterial blood gas (hypoxaemia, respiratory and metabolic acidosis). Pre- and post-ductal pulse oximetry. Blood count and blood culture, because infection may coexist.

**Imaging**
[Chest](https://durgical.com/en/anatomy/region/chest/) X-ray: patchy, coarse asymmetric infiltrates, hyperinflation with flattened diaphragms, and possible air leak. Echocardiography to assess pulmonary hypertension and exclude heart disease.

## Differential diagnosis

- Transient tachypnea of the newborn
- Neonatal pneumonia or sepsis
- Neonatal respiratory distress syndrome
- Persistent pulmonary hypertension of other causes
- Cyanotic congenital heart disease

## Goal of treatment

Establish effective ventilation at birth, maintain oxygenation and perfusion, prevent and treat pulmonary hypertension and air leaks.

## Treatment

**Acute**
Neonatal resuscitation following current guidelines; routine intrapartum or tracheal suctioning of a vigorous or non-vigorous baby is no longer recommended; airway suction only if obstruction is suspected.

**Medical**
Oxygen, CPAP or mechanical ventilation as needed; surfactant replacement (bolus or lavage) in severe cases.

**Medical**
Inhaled nitric oxide for persistent pulmonary hypertension; inotropes and fluids to support blood pressure; antibiotics while infection is excluded.

**Procedure**
Extracorporeal membrane oxygenation (ECMO) in refractory respiratory failure, where available.

**Follow-up**
Close monitoring of gases, saturations, blood pressure and neurological status; minimal handling and a quiet environment.

## Complications

- Persistent pulmonary hypertension of the newborn
- Pneumothorax and other air leaks
- Hypoxic-ischaemic encephalopathy and neurodevelopmental sequelae
- Chronic lung disease and reactive airway disease in childhood
- Death in severe cases

## Prognosis

Most babies recover fully. Mortality and long-term disability are concentrated in severe cases with pulmonary hypertension or brain injury from perinatal asphyxia.

## Prevention

- Good prenatal care and induction of labour in post-term pregnancy
- Intrapartum fetal heart rate monitoring and timely delivery when there are signs of fetal compromise

## Test yourself

Think of the answer, then tap the question to see it.

## Which pregnancies have the highest risk of meconium aspiration syndrome?

Post-term pregnancies and those with fetal distress, placental insufficiency or growth restriction.

## What are the three main mechanisms of lung injury in meconium aspiration?

Airway obstruction with air trapping (ball-valve), surfactant inactivation and chemical pneumonitis.

## Which serious vascular complication often accompanies severe meconium aspiration?

Persistent pulmonary hypertension of the newborn, with right-to-left shunting.

## Is routine tracheal suctioning recommended for babies born through meconium-stained fluid?

No. Current resuscitation guidelines advise standard resuscitation and suction only if the airway is obstructed.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/meconium-aspiration-syndrome/)

## Related conditions

- [Persistent pulmonary hypertension of the newborn](https://durgical.com/en/conditions/persistent-pulmonary-hypertension-of-the-newborn/)
- [Pneumothorax](https://durgical.com/en/conditions/pneumothorax/)
- [Transient tachypnea of the newborn](https://durgical.com/en/conditions/transient-tachypnea-of-the-newborn/)
- [Neonatal respiratory distress syndrome (hyaline membrane disease)](https://durgical.com/en/conditions/neonatal-respiratory-distress-syndrome/)
- [Perinatal asphyxia and hypoxic-ischaemic encephalopathy](https://durgical.com/en/conditions/perinatal-asphyxia-and-hypoxic-ischaemic-encephalopathy/)
- [Chorioamnionitis (intra-amniotic infection)](https://durgical.com/en/conditions/chorioamnionitis/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Meconium aspiration syndrome](https://medlineplus.gov/ency/article/001596.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/meconium-aspiration-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/meconium-aspiration-syndrome/