What does persistent pulmonary hypertension of the newborn (PPHN) mainly result from?

Persistent pulmonary hypertension of the newborn (PPHN) primarily results from a failure to transition normally after birth. At birth, a newborn typically undergoes significant changes in circulation, including the closure of the ductus arteriosus and the onset of normal pulmonary blood flow. In some cases, if there is insufficient relaxation of the pulmonary vasculature or continued high pulmonary vascular resistance, the blood flow to the lungs may remain inadequate, leading to high pressures in the pulmonary arteries.

In typical development, once a newborn is born and takes their first breaths, the lung expands, causing a decrease in pulmonary vascular resistance. If this transition is impaired—perhaps due to issues such as meconium aspiration, congenital diaphragmatic hernia, or other factors that may affect lung function or blood flow—the newborn may experience PPHN, as the high pulmonary pressures cause the right-to-left shunting of blood through openings like the foramen ovale.

Understanding the normal transition is key to grasping how PPHN occurs, as it highlights the critical nature of pulmonary adaptation to extrauterine life.