Aim:  To characterize postnatal changes in serum insulin‐like growth factor‐1 (IGF‐I) in relation to development of bronchopulmonary dysplasia (BPD) in very preterm infants.

Methods:  Longitudinal study of 108 infants with mean (SD) gestational age (GA) 27.2 (2.2) weeks. Weekly serum samples of IGF‐I were analysed from birth until postmenstrual age (PMA) 36 weeks. Multivariate models were developed to identify independent predictors of BPD.

Results:  Postnatal mean IGF‐I levels at postnatal day (PND) 3–21 were lower in infants with BPD compared with infants with no BPD (16 vs. 26 μg/L, p < 0.001). Longitudinal postnatal change in IGF‐I levels (IGF‐I regression coefficient (β)), PNDs 3–21, was lower in infants with BPD compared with infants with no BPD (0.28 vs. 0.97, p = 0.002) and mean IGF‐I during PMA 30–33 weeks was lower in infants with BPD as compared with infants without BPD (22 vs. 29 μg/L, p < 0.001). In a binomial multiple regression model, lower GA, male gender and lower mean serum IGF‐I levels during PND 3–21 were the most predictive risk factors associated with BPD (r² = 0.634, p < 0.001).

Conclusion:  Lower IGF‐I concentrations during the first weeks after very preterm birth are associated with later development of BPD.