Fetal haemoglobin and oxygen requirement in preterm infants: an observational study

Objective To investigate the relationship between the fraction of fetal haemoglobin (HbF(%)) and oxygen requirement as determined by the fraction of inspired oxygen (FiO 2 ) and alveolar–arterial gradient (A–a gradient). Increased alveolar exposure to oxygen may explain the association between decreased HbF(%) and the development of bronchopulmonary dysplasia (BPD). Design Longitudinal, retrospective, observational study. Setting Tertiary-level neonatal intensive care unit, referral centre for southern Sweden. Patients Four hundred forty very preterm infants born before gestational week 30, 2009–2015. Intervention Regular clinical practice. Main outcome measures The FiO 2 and A–a gradient were determined at the time-point of 10 015 arterial blood gas analyses obtained during postnatal days 1–7. The relationship between HbF(%) and FiO 2 and A–a gradient and the modifying influence of other factors affecting haemoglobin oxygen affinity were evaluated. Results We found a significant relationship between a low fraction of HbF and an increase in FiO 2 and A–a gradient, respectively. These relationships remained significant after adjusting for pH, pCO 2 , postnatal age, gestational age and sex. Conclusion These high-resolution data show that decreased HbF(%) during the first postnatal week is associated with increased FiO 2 and A–a gradient in very preterm infants. Increased alveolar exposure to oxygen and resulting oxidative stress may, at least partly, explain the previously reported associations between decreased HbF, blood transfusions and the development of BPD in preterm infants.