Before 34 weeks, one course of antenatal corticosteroids significantly decreases neonatal mortality and morbidity. Courses are repeated every week, because of their alleged loss of efficiency after 7 days, although the relative benefits and risks of repeated courses are poorly known. Data from the literature suggest that improvement in lung function after repeated courses depends on the reduction of the treatment/birth interval and not on the rise in the cumulative dose. These benefits must be balanced against the risk of decreased birth weight induced by repeated courses. Because of their effect on fetal growth, weekly courses of corticosteroids should no longer be given systematically. In clinical practice, pregnancies at high risk of preterm delivery must be reassessed every week before prescribing a new course. Both better understanding of treatment duration of corticosteroids and randomized controlled trials comparing one and multiple courses are needed to improve antenatal management of neonatal respiratory stress syndrome.