Antenatal corticosteroids have their most evident fetal effect on which aspect of surfactant biology?

• A. Flow of fetal lung fluids
• B. Surfactant synthesis
• C. Surfactant secretion response to stimuli
• D. Alveolar capillary network formation

Answer: (B)

Antennatal corticosteroids mainly prime the fetal lung to produce surfactant by increasing the synthesis machinery in type II pneumocytes. They boost the transcription of enzymes and surfactant proteins needed to make the key surfactant lipids, especially dipalmitoyl phosphatidylcholine, so more surfactant is produced and stored before birth. This rise in synthesis directly enhances the lung’s ability to reduce surface tension after birth, improving compliance and lowering the risk of respiratory distress syndrome. While steroids can influence other aspects of lung maturation, the most evident fetal effect in surfactant biology is the upregulation of surfactant synthesis rather than changes in fluid flow, secretion response to stimuli, or vascular development.