Most common in term & post term infants without lung disease

Can happen at any gestational age as a complication of lung disease

To successfully make the transition from a fetal pathway of blood flow to an adult or normal pathway of blood flow following birth requires several events or changes 

Anything that interferes with these events or changes puts the infant at risk for the development of PPHN

Of the transition events, the most important is the establishment of and the maintenance of effective respirations and ventilation