B rief administrations of oxygen are commonly given to term and premature newborns after delivery or before invasive procedures to prevent hypoxaemia. But, to date, no study has validated the usefulness and innocuity of this pre-oxygenation method. Now, in the current issue of the European Respiratory Journal, LOFASO et al.  report the deleterious effects of oxygen administration in newborn mice. The main message of their work is that repeated brief administration of 100% oxygen during a critical window, i.e. the first 3 days of life, was associated with a significant decrease in minute ventilation, owing to an increase in absolute total respiratory time and apnoea duration. Most importantly, these adverse effects increased with repeated exposure. The exposure to a lower concentration of oxygen (30%) produced comparable effects on breathing pattern. In both situations, recovery was observed after return to normoxia. Before analysing the clinical implications of this work, it is worth discussing the methodology of the study.