Adaptation for life after birth: a review of neonatal physiology

Life as a fetus is very different from life after birth. The neonatal period (first 28 days of life or 44 weeks postconception age) is a period of dramatic and rapid physiological changes. These vary from the immediate adaptations to extrauterine life to a consequent gradual maturation of organ function. Questions still exist around this transition concerning the optimal oxygen concentration during resuscitation, methods of respiratory support, facilitation of cardiovascular changes, identification of at-risk infants for problems such as hypoglycaemia and hypothermia, and the role of therapeutic hypothermia. This article combines well established and contemporary information to summarize a systems-based approach to traditional neonatal physiology.