RecruitingDiagnostic testMultidimensional Phenotype Classification in Grade 3 Bronchopulmonary DysplasiaBronchopulmonary Dysplasia (BPD), or chronic lung disease of prematurity, is the most consequential complication of preterm birth and is strong predictor of childhood pulmonary and neurodevelopmental disability, particularly in infants diagnosed with grade 3 BPD (ventilator dependence at 36 weeks' postmenstrual age), the most severe disease form. This study aims to (1) generate the first empirically defined phenotype classification system for grade 3 BPD developed using a rich array of objective and quantitative cardiopulmonary diagnostic, clinical, and biological data; and (2) define the association between phenotype subgroups and neurodevelopmental and respiratory outcomes through 2 years' corrected age.