<qa>  What is the half life of antenatally administered betamethasone?Betamethasone is clinically used as a mixture of betamethasone phosphate 6 mg and betamethasone acetate 6 mg, providing a rapid exposure from the phosphate form and a sustained exposure from the acetate form. Maximal fetal serum level of betamethasone was attained 1-2 hours after ANC treatment 27. The half life of antenatally administered betamethasone is about 12 hours in fetal circulation 1,36. Decrease in the incidence of RDS is evident when ANC is administered between 24 hours and 7 days before delivery. However, the incidence of ICH is decreased even with treatment initiated less than 24 hours prior to delivery 2,3,4. According to the animal studies the short term ANC 24 hours improves the postnatal lung function, decreases the protein leak into the lung and alters postnatal blood pressure regulation in the premature. ANC also seems to augment the postnatal neuroendocrine and endocrine responses to hypoxic challenge 28,29,30. 