Cardiomegaly may be observed as a manifestation of perinatal hypoxia in which condition?

• A. Respiratory distress syndrome
• B. Transient tachypnea of the newborn
• C. Meconium aspiration syndrome
• D. Patent ductus arteriosus

Answer: (C)

When the newborn experiences significant hypoxia from lung disease, the heart has to work against a high resistance in the pulmonary circulation. In meconium aspiration syndrome, inhaled meconium causes airway obstruction and chemical pneumonitis, leading to severe V/Q mismatch and persistent pulmonary hypertension. That elevated pulmonary afterload places strain on the right ventricle, causing it to dilate and the heart to appear enlarged on imaging. This cardiomegaly reflects the heart adapting to hypoxic stress and increased right-sided pressures. Other conditions like respiratory distress syndrome or transient tachypnea of the newborn are more about lung mechanics and edema rather than the pronounced hypoxia-driven pulmonary hypertension that drives right heart enlargement, while PDA mainly causes volume overload. So, cardiomegaly in the setting of perinatal hypoxia is most characteristic of meconium aspiration syndrome.