<p><strong>RATIONALE: </strong>Current diagnostic criteria for bronchopulmonary dysplasia rely heavily on the level and duration of oxygen therapy, do not reflect contemporary neonatal care, nor adequately predict childhood morbidity.</p>

<p><strong>OBJECTIVE: </strong>To determine which of 18 pre-specified, revised definitions of bronchopulmonary dysplasia, that variably define disease presence and severity according to the level of respiratory support and supplemental oxygen administered at 36 weeks postmenstrual age, best predicts death or serious respiratory morbidity through 18-26 months corrected age.</p>

<p><strong>METHODS: </strong>We assessed infants born &lt;32 weeks' gestation between 2011-2015 at 18 centers of the National Institute of Child Health and Human Development Neonatal Research Network.</p>

<p><strong>RESULTS: </strong>Of 2677 infants, 683 (26%) died or developed serious respiratory morbidity. The criteria that best predicted this outcome defined bronchopulmonary dysplasia according to treatment with the following support at 36 weeks postmenstrual age, irrespective of prior or current oxygen therapy: no bronchopulmonary dysplasia, no support (n=773); grade 1, nasal cannula ≤2L/min (n=1038); grade 2, nasal cannula &gt;2L/min or non-invasive positive airway pressure (n=617); and grade 3, invasive mechanical ventilation (n=249). These criteria correctly predicted death or serious respiratory morbidity in 81% of study infants. Rates of this outcome increased stepwise from 10% among infants without bronchopulmonary dysplasia to 77% among those with grade 3 disease. A similar gradient (33%-79%) was observed for death or neurodevelopmental impairment.</p>

<p><strong>CONCLUSIONS: </strong>The definition of bronchopulmonary dysplasia that best predicted early childhood morbidity categorized disease severity according to the mode of respiratory support at 36 weeks postmenstrual age, irrespective of supplemental oxygen use. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial License 4.0 (http://creativecommons.org/licenses/by-nc/4.0/).</p>