It is nearly 25 years since Liggins and Howie first reported the maturational benefits of antenatal corticosteroids given to mothers of preterm infants.1 They reported reduced incidence of respiratory distress syndrome (RDS) in preterm infants delivered to mothers treated with antenatal steroids. Since then, several other studies have reported similar benefits for antenatal corticosteroids. Indeed, Crowley2 has reported a meta-analysis of 15 randomised trials, conducted between 1972 and 1994, which studied the use of antenatal corticosteroids in preterm labour. Overall, the incidence of RDS was halved in infants delivered to mothers who had received antenatal corticosteroids compared with those born to mothers treated with placebo. Secondary analysis clearly showed that when antenatal corticosteroids are given between 24 hours and 7 days before delivery, the odds ratio is 0.35 (95% CI 0.26–0.46). This is reduced to 0.8 (95% CI 0.56–1.15) if antenatal corticosteroids are given at less than 24 hours before delivery, and to 0.63 (95% CI 0.38–1.07) if given more than seven days before delivery. Clearly, antenatal corticosteroids require at least 24 hours to exert their effects.

Clinical trials of postnatal systemic corticosteroids in established chronic lung disease of prematurity (CLD) have been thoroughly reviewed by Ehrenkranz and Mercurio.3 At least nine randomised controlled trials of parenteral or oral dexamethasone have been reported for infants aged 2–6 weeks of postnatal age.4-12 All except two5 10 were devoted exclusively to intubated babies. The UK collaborative trial, one of the largest with 285 babies, covered a wide clinical spectrum of disease.5 The main outcome measures in most …