Condition of term or postterm newborn where circulation fails to transition from fetal to normal perinatal circulation, maintaining a dangerously high pulmonary vascular resistance, in the absence of congenital heart disease. This reduces pulmonary blood flow in the neonate and creates a right-to-left shunting over a patent ductus arteriosus or patent foramen ovale. Characterized by respiratory distress, cyanosis, tachypnea, and hypoxemia. Symptoms may be mild or severe. Poor oxygenation can lead to organ dysfunction and higher risk of morbidity and mortality. Causes include meconium aspiration, pulmonary hypoplasia, respiratory distress syndrome, congenital diaphragmatic hernia, and infection possibly leading to sepsis or pneumonia (often group B streptococcal).

An association has been drawn to maternal use of antidepressants in the third trimester. However, studies linking maternal use of NSAIDs had mixed results.

Management includes cardiorespiratory intervention, treatment of associated conditions (such as antibiotics for neonatal infection), treatment of acidosis, and monitoring of oxygenation level. Treatments to maintain targeted oxygen saturation level include mechanical ventilation, supplemental oxygen, and assisted ventilation. Vasodilators may be prescribed to regulate vascular resistance. In extreme cases, extracorporeal membrane oxygenation may be required.