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Prophylactic corticosteroids
The administration of certain corticosteroids to women at risk of preterm delivery causes a considerable reduction in the risks of complications of prematurity such as respiratory distress syndrome, intraventricular haemorrhage and perinatal death. The effects are most clearly demonstrated after 28 weeks and before 32–34 weeks of gestation, and in babies delivering 1–7 days after the intervention. No adverse effects on the baby have been found. Corticosteroid regimens shown to be effective include: betamethasone 12 mg intramuscularly, 2 doses 24 hours apart; or dexamethasone 6 mg intramuscularly 4 doses 12 hourly. Studies using hydrocortisone gave conflicting results. Studies using methyl-prednisolone were excluded because this steroid has been shown not to cross the placenta to the fetus.

The Cochrane review was last updated in 1999. The search strategy of the Cochrane Pregnancy and Childbirth Group was used. The single author did data extraction. Some trials with large proportions of exclusions after randomization were included on the basis that there was no evidence of selective exclusions from either group. Additional information which would be useful would be the geographical location of studies and sub-group analysis by trial quality.

Repeat doses of prenatal corticosteroids
This review included trials of repeat corticosteroid therapy in women who had received a single course of corticosteroids 7 or more days previously. Three studies from North America with a total of 551 women were included. All three were of high methodological quality and all used two doses of betamethasone 12 mg, repeated weekly. One or more repeat courses of corticosteroids were associated with reduced severe lung disease (relative risk [RR]: 0.64; 95% confidence interval [CI]: 0.44–0.93) and fewer neonates receiving surfactant (RR: 0.65; 95% CI: 0.46–0.92). No other outcomes were statistically significant. However, available data from the studies did not give the review sufficient statistical power to assess important rare outcomes such as perinatal/infant death (RR: 0.53; 95% CI: 0.18–1.57). The authors therefore concluded that there was insufficient evidence regarding the potential benefits and risks to justify the use of repeated doses of corticosteroids in clinical practice, and that further trials were needed. The results of the several ongoing trials are awaited.

The search strategy of the review was comprehensive. Trial quality was rigorously assessed. Data were extracted by two reviewers independently, and double-entered. The data are presented clearly. Useful sub-group analysis is planned for effect modifiers, though currently not possible due to insufficient data.

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