Caption: Peripheral pulmonary stenosis (PPS)
Text: a soft SEM murmur heard mostly along the upper left sternal border with radiation to both axillae. Transient PPS is a common murmur in newborns and is more frequent in premature infants. In the fetus, only about 10% of the combined ventricular output passes into the branch pulmonary arteries (compared to 100% postnatally). Also, the chest cavity is small. This leads to a mild hypoplasia and an increased angulation of the branch pulmonary arteries. PPS usually disappears at 4-6 months of age. Even though most cases of PPS are benign, it is not called "innocent" as it could also be associated with pathological conditions such as congenital rubella, Alagille or Noonan syndromes.