Background Endothelin-1 (ET-1) is a potent pulmonary vasoconstrictor, involved in lung injury and remodelling. ET-1 can be estimated by measuring its stable by-product, C-terminal pro-ET-1 (CT-proET-1), in plasma.

Aims To investigate CT-proET-1 values in very preterm infants (gestational age <32 weeks) from birth to postmenstrual age (PMA) of 36 weeks, and their relationship with lung injury and bronchopulmonary dysplasia (BPD).

Methods Prospective cross-sectional study of 391 CT-proET-1 measurements (fully automated immunoflorescent assay) from 267 very preterm infants. Measurements were performed at birth (n = 72 infants), on day of life (DOL) 2 (n = 89), on DOL 6 (n = 49), on DOL 28 (n = 106), and at PMA 36 (n = 75). Trial registration: ClinicalTrials.gov NCT01644981.

Results CT-proET-1 values were (median) 151 pmol/L (IQR 118–186) at birth, peaked on DOL 2 (319 pmol/L (235–382)), and declined thereafter to 214 pmol/L (148–293) on DOL 6, 184 pmol/L (149–233) on DOL 28, and 150 pmol/L (118–188) at PMA 36. Infants with BPD had higher CT-proET-1 values on DOL 2 (p = 0.001), DOL 6 (p < 0.001), and DOL 28 (p = 0.007), with no differences at birth and PMA 36 as compared to those without BPD. CT-proET-1 on DOL 6 was significantly correlated with days of mechanical ventilation, nasal CPAP, and oxygen requirement (Spearman’s Rs 0.657, 0.713, 0.745, respectively, p < 0.001 each). Moderate correlations were found for the same parameters on DOL 2 and DOL 28 but not for birth and PMA 36.

Conclusions The levels and the pattern of CT-proET-1 increase during the first week of life might serve as an early marker of BPD.