Bronchopulmonary dysplasia is a chronic lung disease which affects premature infants. Premature infants who require treatment with supplemental oxygen or require long-term oxygen are at a higher risk. The alveoli that are present tend to not be mature enough to function normally. It is also more common in infants with low birth weight and those who receive prolonged mechanical ventilation to treat respiratory distress syndrome. It results in significant morbidity and mortality. The definition of bronchopulmonary dysplasia has continued to evolve primarily due to changes in the population, such as more survivors at earlier gestational ages, and improved neonatal management including surfactant, antenatal glucocorticoid therapy, and less aggressive mechanical ventilation.