<P> Dexamethasone and betamethasone are the corticosteroids used for the purpose although the former is recommended over the latter based on its efficacy , safety , wide availability , and low cost in spite of some counter-logic . Betamethasone , on the other hand , is preferred over dexamethasone because it is thought to have better prophylaxis of brain softening of premature fetus . They are used with the intention to help the lungs of a premature fetus develop before the fetus comes out . They are given when the fetus is expected to be delivered within 24 to 48 hours . Treatment consists of 2 doses of 12 mg of betamethasone given intramuscularly 24 hours apart or 4 doses of 6 mg of dexamethasone given intramuscularly 12 hours apart . Optimal benefit begins 24 hours after initiation of therapy and lasts 7 days . Antenatal steroids are currently used up to 36 weeks in some parts of the world obstetric practice . </P>
when are steroids given for fetal lung maturity
when the fetus is expected to be delivered within 24 to 48 hours