Adaptation for life: a review of neonatal physiology

The neonatal period (first 28 days of life or 44 weeks postconception age) is a period of the most dramatic and rapid physiological changes seen in humans. They vary from the immediate changes in the respiratory and cardiovascular systems to a gradual maturation of the hepatic, haematological and renal systems. These adaptations support life during the development from intrauterine physiology to adult physiology. This article describes neonatal physiological changes in a system-based approach, including the changes that may extend beyond the neonatal period.