**Question:** A 26 year old third gravida mother delivered a male baby weighing 4–2 kg at 37 weeks of gestation through an emergency caesarean section, for obstructed labour. The child developed respiratory distress one hour after birth. He was kept nil per orally (NPO) and given intravenous fluids. He maintained oxygen saturation on room air. No antibiotics were given. Chest radiograph revealed fluid in interlobar fissure. Respiratory distress settled by 24 hours of life. What is the most likely diagnosis?

A. Respiratory distress syndrome (RDS)
B. Pulmonary hypoplasia
C. Congenital pneumonia
D. Congenital heart disease

**Correct Answer:** A. Respiratory distress syndrome (RDS)

**Core Concept:**
Respiratory distress syndrome (RDS) is a condition in premature infants that occurs due to immaturity of the lungs and surfactant deficiency. Surfactant is a substance that helps prevent the lungs from collapsing after birth. In RDS, surfactant production is inadequate, leading to hypoxemia (low oxygen levels), hypercapnia (elevated carbon dioxide levels), and pulmonary hypertension, resulting in the clinical presentation described in the question.

**Why the Correct Answer is Right:**
In this case, the child developed respiratory distress one hour after birth and showed improvement over the next 24 hours. The other options are not supported by the clinical picture.

**Why Option B is Incorrect:**
Pulmonary hypoplasia refers to an abnormal reduction in lung tissue and is not relevant in the scenario described. The child's respiratory distress improved over time, suggesting that the issue is not due to underdeveloped lungs.

**Why Option C is Incorrect:**
Congenital pneumonia is an infection of the lungs, which did not match the described clinical presentation in this scenario. The child's respiratory distress resolved within 24 hours without antibiotics, further supporting this diagnosis.

**Why Option D is Incorrect:**
Congenital heart disease is unrelated to the respiratory distress described in this scenario. The child's respiratory distress improved over time, suggesting that the issue is not caused by heart-related problems.

**Why Option A is Correct:**
Respiratory distress syndrome (RDS) is the most suitable diagnosis for the described clinical presentation. The child's respiratory distress started shortly after birth and resolved within 24 hours without antibiotics, indicating the issue is likely due to immaturity of the lungs and surfactant deficiency, which is characteristic of RDS. The child did not have an underdeveloped lung issue (B), an infection (C), or congenital heart disease (D). The clinical improvement over time supports the diagnosis of RDS as well.

**Clinical Pearls:**
1. RDS typically presents with respiratory distress, cyanosis, grunting, and intercostal retractions in premature infants.
2. In RDS, the chest radiograph may show hyaline membrane disease with hyperinflation, interstitial and alveolar edema, and sometimes pneumothorax (air in the pleural space) and hyaline membranes.
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