Typically, a fetus experiences pulmonary hypertension in utero since it is relying on the placenta for oxygen rather than its lungs. When the fetus is born, it is no longer attached to the placenta and must use the lungs to receive oxygen. To facilitate this change from fetus to newborn, the baby must change from a state of high PVR to low PVR, allowing for increased blood flow to circulate throughout the body. This inability of the newborn to adapt to these changes is caused by various processes, such as: * Normal vascular anatomy with functional vasoconstriction: This has a good prognosis, as it is reversible. Causes include hypoxia, meconium aspiration, and respiratory distress syndrome. Left untreated, this can lead to hypoxic respiratory failure (HRF). * Decreased diameter of pulmonary vessels with hypertrophy of vessel walls: This has a poor prognosis, as it is a fixed abnormality. Causes include post-term pregnancy, placental insufficiency, and NSAID use by the mother. * Decreased size of pulmonary vascular bed: This has a poor prognosis, as it is a fixed abnormality. It is caused by space occupying lesions such as pleural effusions and diaphragmatic hernias. * Functional obstruction of pulmonary blood flow: This has a good prognosis if it is reversible. Causes include polycythemia and hyperfibrinogenemia.
Persistent fetal circulation
Alveolar capillary dysplasia
Neonatal sepsis
Foetal cerebral redistribution
Umbilical cord compression
Shaken baby syndrome
Fetal distress
Placental insufficiency