Early decrease in fetal haemoglobin (HbF) is an indicator of loss of endogenous blood components that might have predictive value for development of bronchopulmonary dysplasia (BPD).

The link between HbF and BPD has not been evaluated.

Tertiary level neonatal intensive care unit, referral centre for Southern Sweden. Patients 452 very preterm infants (<30 gestational weeks) born 2009–2015.

Main outcome measures: Mean HbF, haemoglobin (Hb) and partial oxygen pressure (PaO2) levels calculated from 11 861 arterial blood gas analyses postnatal week 1. Relationship between HbF (%) and BPD (requirement of supplemental oxygen at 36 weeks’ postmenstrual age) and the modifying influence of PaO2 (kPa) and total Hb (g/L) was evaluated.