Among infants with RDS, ET-1 was significantly higher in those who later developed BPD.34 Furthermore, ET-1 was significantly elevated in tracheal aspirates of preterm infants on DOL 1, 3, and 7 who subsequently developed BPD.35 Only few studies evaluated CT-proET-1 for BPD development. Here, EDN1 is linked to bronchopulmonary dysplasia.