Final answer:
Betamethasone is the corticosteroid that enhances fetal lung maturity and reduces the risk of infant respiratory distress syndrome.
Step-by-step explanation:
The corticosteroid whose purpose is to release surfactant and enhance fetal lung maturity is Betamethasone. The mother should receive 12 mg IM (intramuscular) injections 24 hours apart. This treatment helps in the development of the lungs and assists in reducing the risk of infant respiratory distress syndrome.