Small proline-rich protein 2E (SPRR2E), secretory leukocyte peptidase inhibitor (SLPI) and gamma-glutamyl hydrolase (GGH) were all significantly less abundant in the BPD group (− 0.92, p = 0.04; − 2.08, p = 0.04; − 0.79, p = 0.03 respectively); however, these were detected in < 25% of the samples. Here, SLPI is linked to bronchopulmonary dysplasia.