Abstract: Preterm birth is the leading cause for neonatal mortality and morbidity. Antenatal corticosteroids （ACS） can significantly reduce premature mortality and risks of respiratory distress syndrome and intraventricular hemorrhage. Currently a single dose of dexamethasone or betamethasone is recommended for pregnant women at high risks of preterm delivery between 24 and 34 gestational weeks. The long-term safety for repeated courses of ACS therapy is uncertain，therefore the therapy of repeated courses of ACS is not routinely recommended. For patients at high risks of preterm delivery within the coming week，a single“rescue course”of ACS can be considered to be given，i.e. a repeated course of routine ACS. The long-term safety of ACS before selectively caesarean section before 39 gestational week remains questionable. The therapeutic regimes and clinical effects for the single and the repeated course of ACS therapies have been reviewed.

Key words: Premature birth, Infant mortality, Respiratory distress syndrome, newborn, Antenatal corticosteroids