Prenatal glucocorticoids are effective in promoting fetal pulmonary maturation and therefore in preventing RDS. TRH in animals increases the secretion of phospholipids, pulmonary compliance promotes pulmonary morphologic maturation and reduces the passage of proteins to the alveolus. Experimentally TRH+ CS have a synergistic action. Clinical controversy exists in relation to the usefulness of the combined therapy. Primary objective to determine whether prenatal administration of TRH + CS plus postnatal surfactant in pregnancies ≤32 weeks may reduce the incidence of RDS, mortality and chronic lung disease. The secondary objectives referred to complications of RDS. A controlled, double blinded, randomized clinical trial was performed in 8 Clinical Hospitals in Chile, during 3 years. The study group received TRH 400ug: the placebo group normal saline, both diluted in 50ml of normal saline administered in 20-30 minutes IV every 8 hours: 4 doses. Both groups received betamethasone 12mg 1M every 24 hours; 2 doses. All premature infants ≤1000g received surfactant (Exosur). Premature infants< 1000g received surfactant only with clinical evidence of RDS (rescue), with a maximum of 2 doses. Groups were similar in gestational age, birthweight, maternal morbidity, tocolytics, route of delivery, gender, APGAR score and interval from randomisation to delivery. 85-86% received 4 doses of TRH and 86-88% 2 doses of CS. Table

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There were no differences in secondary results.