The fetal effect seen with antenatal corticosteroids is most evident upon which process?

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

Answer: (B)

Antenatal corticosteroids mainly accelerate fetal lung maturation by increasing surfactant synthesis. They cross the placenta and stimulate type II pneumocytes to upregulate the production of surfactant components, including phospholipids like DPPC and surfactant proteins. This elevates the amount of surfactant available at birth, lowering alveolar surface tension and helping prevent collapse, which is the key reason these steroids reduce RDS in preterm infants. While surfactant secretion in response to stimuli is important for function, the primary and most evident fetal effect is enhanced synthesis. Alveolar capillary formation and fetal lung fluid flow are less directly affected by these drugs in the immediate context of surfactant maturation.