Single-course treatment with antenatal corticosteroids has been shown to enhance fetal maturation before preterm birth and to improve outcomes for the preterm infant. Based on this success, practitioners expanded use of the treatment to repeated courses of antenatal corticosteroids ahead of evidence demonstrating benefit and excluding harm. Experiments with animals and cohort studies have provided a body of evidence suggesting that repeated doses may further improve lung maturation but may be accompanied by deleterious effects on the developing brain and other organs. Randomised controlled trials of repeated treatments to date have provided mixed evidence but in general may indicate a small benefit in terms of postnatal lung function, but this is accompanied by restricted growth which may include the brain. In view of the well-established role that corticosteroids are known to play in brain development, and the marginal difference that repeated courses may make to outcome in the context of modern neonatal care, antenatal corticosteroid treatments should be restricted to single-course treatment.