Pulmonary vascular disease (PVD) summarizes all congenital or acquired pathologies that affect the pulmonary vasculature. One of these is pulmonary hypertension (PH), which is characterized by a mean pulmonary artery pressure of ≥25 mmHg in rest, or ≥30 mmHg during exercise. This definition applies for adults and children .
Pulmonary hypertension is associated with a variety of diseases with different pathogenesis. A diagnostic classification of PH, based on the different causes, was made in 2003 .
There is some ambiguity about pulmonary hypertension in newborns (PHN). Both primary and secondary PHN are often collectively referred to as persistent pulmonary hypertension of the newborn (PPHN). In the last decades a variety of different terms describing PPHN: persistence of the fetal circulation , persistent transitional circulation  persistence of the fetal cardiopulmonary circulatory pathway , progressive pulmonary hypertension  and persistent pulmonary vascular obstruction . They all describe a failure or delay in the transition from fetal to neonatal circulation, exemplified by the failure of decreasing the PVR after birth and abnormalities in the pulmonary vasculature. Clinically, each form of pulmonary hypertension in the newborn is referred to as PPHN.
In the WHO diagnostic classification of pulmonary hypertension, persistent pulmonary hypertension of the newborn is classified together with pulmonary arterial hypertension (Group I) and pulmonary hypertension that is associated with lung disease and hypoxemia is classified in group III. In this group there is a subgroup for abnormal development, for example in congenital diaphragmatic hernia (CDH).
In this review we will focus on pulmonary hypertension in newborns in relation to therapeutic strategies.