In this study, BPD was defined as oxygen dependency at 28 days with ‘radiographic changes.’ Eighteen infants developed BPD and had significantly increased levels of TGF-β1 in tracheal aspirates, when compared to those with RDS and the controls.(51) TGF-β1 was also noted to be increased in one study assessing the levels of seven cytokines in ventilated babies in the first 5 days of birth. This evidence concerns the gene TGFB1 and bronchopulmonary dysplasia.