Effects of antenatal corticosteroids given prior to 26 weeks' gestation: a systematic review of randomized controlled trials.

Although it is generally accepted that antenatal corticosteroids reduce neonatal complications after preterm labor, it is unclear at what gestational age this effect starts to occur. We conducted a systematic review of the literature to determine the effects of antenatal corticosteroids given to women at risk of preterm birth <26 weeks' gestation. Two reviewers independently searched electronic databases and the Cochrane Library for randomized controlled trials including women at imminent birth at a gestational age <26 weeks. Nine randomized trials were included. Meta-analyses and meta-regression of trials including participants with a lower gestational age revealed no significant reduction of neonatal mortality and morbidity in the corticosteroid group as compared with nonintervention, in contrast to clear evidence of beneficial effects in trials including women given corticosteroids at a later gestational age. A gestational age-dependent effect of antenatal corticosteroids on neonatal outcomes with lesser treatment benefits in patients <26 weeks' gestational age appears to exist. There is no evidence from randomized controlled trials to support or refute the recommendation of administrating antenatal corticosteroids to women at risk of preterm birth <26 weeks' gestation.