A 32-week gestation male infant born to a mother with inadequate antenatal care presents with grunting, nasal flaring, and intercostal retractions within 2 hours of birth. Chest X-ray shows a ground-glass appearance with air bronchograms. What is the most common cause of respiratory distress in this preterm infant?

Explanation

## Most Common Cause of RDS in Preterm Infants **Key Point:** Surfactant deficiency (Respiratory Distress Syndrome or Hyaline Membrane Disease) is the most common cause of respiratory distress in preterm infants, particularly those <34 weeks gestation. ### Pathophysiology Surfactant is a lipoprotein complex synthesized by type II pneumocytes. It reduces alveolar surface tension and prevents alveolar collapse during expiration. - **Surfactant production begins:** ~24 weeks gestation - **Adequate levels achieved:** ~35 weeks gestation - **Deficiency leads to:** Atelectasis → increased work of breathing → respiratory failure ### Clinical Features of RDS | Feature | Timing | Presentation | |---------|--------|---------------| | **Onset** | Within 2–4 hours of birth | Immediate respiratory distress | | **Signs** | Grunting, flaring, retractions | Progressive over first 24–48 hours | | **CXR** | Ground-glass appearance | Air bronchograms, white-out in severe cases | | **Risk factors** | Prematurity, maternal diabetes, C-section without labor | Perinatal asphyxia | ### High-Yield Risk Factors **Mnemonic: CRIB-SURF** (risk factors for surfactant deficiency) - **C**esarean delivery without labor - **R**ecent maternal diabetes - **I**ntrauterine growth restriction (IUGR) - **B**rief gestation (<34 weeks) - **S**econd-born twin - **U**remia in mother - **R**hesus incompatibility - **F**emale infant (paradoxically, males have delayed lung maturity) ### Management Principles 1. **Antenatal:** Maternal corticosteroids (betamethasone) accelerate fetal lung maturity 2. **Postnatal:** Exogenous surfactant replacement (Poractant alfa, Beractant) 3. **Supportive:** CPAP or mechanical ventilation, oxygen therapy **Clinical Pearl:** The ground-glass appearance on chest X-ray is pathognomonic for RDS and reflects widespread atelectasis with patent airways (air bronchograms visible). **High-Yield:** Surfactant replacement therapy has dramatically reduced mortality in preterm infants. Early administration (within 1–2 hours of birth) is associated with better outcomes.