 The administration of glucocorticoids during the postnatal period with action both glucocorticoid and mineralocorticoid enables a reduction in the incidence of bronchopulmonary dysplasia severe. However, such treatment is associated with an increased incidence of neurodevelopmental effects related to activation of the glucocorticoid pathway. Using a specific mineralocorticoid agonist should preserve the beneficial effects without the adverse effects observed. The results of this pilot study will in a second time to consider a clinical trial Phase III national or international evaluating the significant reduction of these complications after substitution by Fludrocortisone the first week of life in the great premature. These results should have a major medical and economic impact. Indeed, neonatal morbidity indicators intraventricular hemorrhage, patent ductus arteriosus, bronchopulmonary dysplasia and enterocolitis necrotizing are associated with the subsequent development of neurodevelopmental sequelae cerebral palsy and or cognitive impairment at the age of two and five years. 