Last updated:
March 31, 2026
Neonatal respiratory distress syndrome (NRDS) is the most common cause of respiratory distress in preterm neonates. It is caused by insufficient surfactant production at < 34 weeks of gestation.
Antenatal steroids reduce the risk of neonatal respiratory distress syndrome by 40%.
- Predisposing factors
- Prematurity
- < 34 weeks of gestation, especially < 28 weeks
- Maternal diabetes – delayed surfactant due to fetal hyperinsulinism
- Perinatal asphyxia – hypoxia impairs surfactant production
- Caesarean section, or **precipitous delivery due to lack of stress-induced steroid surge
- Multiple gestation, particularly the second twin
- Cold stress
- History of NRDS in a sibling
- Male sex
- Prematurity
- Pathophysiology
- Surfactant is produced by type II pneumocytes. Production begins at 20 – 24 weeks, and mature levels are reached at 35 weeks of gestation. Corticosteroids increase surfactant production
- Surfactant helps to reduce alveolar surface tension and prevent atelectasis
- In preterms < 34 weeks, surfactant synthesis is insufficient. This causes increased surface tension and atelectasis during exhalation
- Persistent atelectasis causes endothelial damage, causing fibrin and proteins to leak into the alveoli and form a hyaline membrane
- Atelectasis and hyaline membrane formation cause ventilation-perfusion (V/Q) mismatch, which leads to hypoxemia and cyanosis
- Pulmonary vasoconstriction from hypoxia can worsen the ventilation-perfusion mismatch
- Signs and symptoms
- Respiratory distress (tachypnea, intercostal indrawing, grunting, cyanosis, flaring of nasal alae)
- On auscultation
- Diminished air entry
- Basal fine crepitations
- Antenatal investigations
- Lecithin/sphingomyelin ratio
- 2.5 = Mature lungs
- 1.5-2 = Transitional lung with increased risk of RDS
- < 1.5 = Immature lung with risk of severe RDS
- Saturated phosphatidylcholine
- <500 μg/dL = Immature lung with high risk of RDS
- 500 μg/dL = Mature lung
- Lecithin/sphingomyelin ratio
- Post-natal investigations
- Chest X-ray:
- Diffuse bilateral reticulonodular infiltrates (diffuse ground glass appearance),
- Air bronchograms (contrast of aerated airways vs collapsed airways),
- Small lung volumes
- Severe RDS shows opacification of both lungs
- Arterial blood gases:
- Hypoxemia
- Hypercapnia
- Respiratory and metabolic acidosis
- UECs
- Hyponatremia due to fluid retention
- CBC + CRP: evaluate the possibility of early-onset NNS in a preterm baby (clinically indistinguishable from RDS)
- Shake test: Done within one hour of life to determine the amount of surfactant present. 0.5ml of gastric aspirate + 4ml of Normal saline + 0.5ml of alcohol are mixed and shaken; check for presence of bubbles
- Absence of bubbles – absent surfactant, hence high risk of RDS
- Incomplete bubbles – intermediate risk of surfactant
- Double row of bubbles or more – no risk of RDS
- Chest X-ray:
- Prevention
- Antenatal prophylaxis:
- Betamethasone or dexamethasone is administered to mothers in preterm labor, at least 24 hrs before delivery.
- This accelerates surfactant production.
- Avoid risk factors
- Antenatal prophylaxis:
- Supportive treatment
- Supplemental O2 via nasal CPAP for mild cases
- Mechanical intubation for severe cases
- Incubator care
- Frequent vital monitoring
- Adequate fluids and feeds
- Definitive treatment
- Intubation for exogenous surfactant administration: definitive treatment. 3-5ml per kg per dose given at 6-12 hour intervals
- Prophylactic exogenous surfactant for all neonates born ≤ 27 weeks
- Empiric antibiotics should be given since NRDS is hard to differentiate from congenital pneumonia
- Indications for surfactant therapy
- FiO2 required >30%
- Recent intubation
- SAS score < 4
Differentiating TTN from NRDS
| Feature | Transient Tachypnea of the Newborn (TTN) | Neonatal Respiratory Distress Syndrome (NRDS) |
|---|---|---|
| Pathophysiology | Delayed clearance of lung fluid | Surfactant deficiency → Alveolar collapse |
| Gestational Age | Term or late preterm (≥35 weeks) | Preterm (<34 weeks) |
| Risk Factors | C-section, maternal diabetes, macrosomia, inadequate thoracic squeeze | Prematurity, maternal diabetes, and perinatal asphyxia |
| Onset of Symptoms | Within hours after birth | Immediately after birth |
| Respiratory Rate | Tachypnea (>60 bpm) | Tachypnea (>60 bpm) |
| Oxygen Requirement | Minimal, resolves in 24-72 hours | Progressive hypoxia needs CPAP or mechanical ventilation |
| Chest radiograph Findings | Hyperinflation, fluid in fissures, perihilar streaking | Ground-glass opacities, air bronchograms, and low lung volume |
| Treatment | Supportive (O₂, CPAP if needed) | Surfactant, CPAP, ventilation if severe |