Antenatal steroids: can we optimize the dose?

The beneficial effects of antenatal steroids in women at risk of preterm birth are evident. A dose of 24 mg appears sufficient, but there are insufficient data to recommend betamethasone or dexamethasone, a single steroid dose, the optimal interval between doses and repeated courses, the gestational age at which treatment is beneficial and the long-term effects of steroid treatment. This review addresses these aspects of antenatal steroid treatment.

Although the 12-h and 24-h dosing intervals are equivalent with respect to prevention of respiratory distress syndrome, the former enables the completion of treatment in 50% more neonates delivered prematurely. Reducing the single steroid dose in patients at risk for premature birth reduces the associated maternal side effects. An inverse relationship has been demonstrated between the number of corticosteroid courses and foetal growth. The reduced size of exposed foetuses has been attributed to birth at earlier gestational ages and decreased foetal growth. Evidence suggests that antenatal exposure to synthetic glucocorticoids in term-born children has long-lasting effects, which may have important implications in the recommendation of steroids before elective caesarean at term.

The short-term and long-term effects of the dosage regimen on the pregnant mother and foetus remain unclear.