To precisely delineate the timing and contribution of inflammation to bronchopulmonary dysplasia (BPD) in preterm infants during the neonatal period.

Longitudinal study of blood inflammatory biomarkers (interleukin [IL]-6, IL-8, and granulocyte colony-stimulating factor) measured between birth and 42 days of age, at high temporal (daily) resolution, in infants born at or below 30 weeks of gestation. Cytokine predictors of BPD at 36 weeks postmenstrual age were adjusted for infant-specific and time-dependent factors, using hierarchical mixed effects regressions models.

A total of 1518 data points were obtained in 62 infants (mean gestational age of 27 weeks). Infants who developed BPD later on presented increased inflammation after birth compared with infants without BPD. Inflammation was sustained, with gradual attenuation over 2 weeks (IL-8: OR: 6.5 [95% CI: 1.8-24]; granulocyte colony-stimulating factor: 3.3 [1.5-7.6]) and was higher in boys and in infants of lower birth weight. This inflammation preceded the clinical increased requirement in supplemental oxygen characteristic of BPD, and preceded the peak occurrence of neonatal sepsis or necrotizing enterocolitis.

Systemic inflammation occurs early in the neonatal period and precedes clinical symptoms in infants with BPD. These data provide a discrete vulnerability window period, supporting a role for targeted intensive care interventions during the early phase of BPD.