Pulmonary hypoplasia is incomplete development of the
lungs, resulting in an abnormally low number or size of
bronchopulmonary segments or
alveoli. A
congenital malformation, it most often occurs secondary to other
fetal abnormalities that interfere with normal development of the lungs. Primary (
idiopathic) pulmonary hypoplasia is rare and usually not associated with other maternal or fetal abnormalities.