The respiratory system mainly performs oxygenation and carbon dioxide clearance. During intrauterine life, the development of the respiratory system starts from a single primitive bud, which divides into the subsequent primitive airways. These primitive airways gradually divide further and elongate, and this phase is followed by the formation of the alveoli which continues long after birth until childhood and into adolescence. At birth, the source of oxygenation rapidly transitions from the placenta to the newborn lungs following a series of swift cardiorespiratory events and adaptations. Failure of this transition might lead to a persistent elevation in the pulmonary artery pressure which in the newborn could cause shunting of deoxygenated blood and hypoxaemia.