Population characteristics and early respiratory morbidity
The children born preterm had a median gestational age at birth of 26 weeks+1 day, 73% were born extremely preterm, i.e. before 28 weeks, and 63% had a diagnosis of BPD (Table 1). In comparison to children born preterm without BPD, children with BPD had a lower gestational age at birth, a lower birth weight and were more often male. In the neonatal period, they were more often treated with surfactant and were more often mechanically ventilated and for longer periods (E-table 1). Smoking during early pregnancy was only reported in 13% of mothers to preterm infants.