Although there is evidence that the use of prebirth steroids promote maturity of premature newborn, in the United States of America it has been estimated that only 50% of the women who have had a premature delivery (with babies with weight between 501 and 1500 g) have been treated with steroids. We analyzed the morbimortality and the need of assisted ventilation in 91 premature newborns with gestational age of less than 34 weeks and weight of 1,500 g or less. They were divided in two groups: one group included 50 newborns whose mothers received at least one full course of steroids and the other group included 41 newborns whose mothers did not receive it. Newborn pathologies, the need of assisted ventilation and the mortality were higher in the group that did not receive prebirth steroids. We conclude that the use of prebirth steroids diminishes the morbimortality of the premature newborn.