Although the majority of newly born babies will establish normal respiratory and circulatory function without help, 1-2% might run into difficulties because of a disturbance in the normal adaptive processes required for a smooth transition from intrauterine to extrauterine life. An understanding of the normal and abnormal perinatal physiology is important to appreciate the practical differences in the approach to caring for such babies, and also for avoiding actions that might be detrimental in the longer term.