• Alveolar–arterial oxygen pressure difference;
  • Bronchopulmonary dysplasia;
  • Extreme prematurity


Aims:  To determine how the ability to oxygenate the blood develops after birth in infants of extremely low gestational age (ELGANs) and to find risk factors for chronic lung disease.

Method:  A prospective, population-based, cohort study was undertaken in one tertiary-care centre. The alveolar–arterial oxygen pressure difference (AaDO2) was monitored.

Results:  Of 41 survivors, 21 had a period of normal lung function in the first week of life, after which oxygenation deteriorated. Low gestational age and low Apgar score at 5 min were found to be strong and independent predictors of AaDO2 in the first month of life. Mechanical ventilation did not appear as a risk factor. Lung function at 36 weeks of gestation and duration of oxygen treatment could be better predicted by the severity of lung disease in the first month than by gestational age at birth.

Conclusions:  Difficulty in oxygenation was a general observation in ELGANs and not only a particular subset. Gestational age and Apgar score were independent predictors of the degree of difficulty over the first month of life. As oxygenation failure often developed after a few days, the process may be possible to treat or prevent once the pathogenesis is known.