Antenatal corticosteroid treatment: factors other than lung maturation.

Antenatal corticosteroid (CS) therapy improves both fetal lung mechanism and gas exchange due to accelerated morphologic development of type one and two pneumocytes. This therapy also enhances the production of surfactant binding proteins and fetal lung antioxidant enzymes. In women with threatening preterm delivery, a single course is advocated between 24 and 34 weeks' gestation with either betamethasone (two doses of 12 mg 24 h apart) or dexamethasone (four doses of 6 mg at 12-h intervals). Such treatment reduces the rate of respiratory distress syndrome, comorbidity, and mortality in neonates in the first 48 h of life. The optimal time interval between CS administration and delivery is reported to be 1-7 days. Weekly repeat courses reduce the occurrences and severity of respiratory diseases but are associated with reduce fetal growth. Multiple courses should be avoided. However, a repeat course should be considered in women at risk of preterm birth 7 or more days after an initial course in women who remain at risk of preterm birth <34 weeks' gestation. CS may be harmful in growth restricted fetuses associated with an absent or reversed end-diastolic UA flow since they are at increased risk of acidosis and perinatal death. The purpose of this publication is to update and highlight antenatal CS therapy.