Pulmonary stenosis (also called pulmonic stenosis) is when the pulmonary valve (the valve between the right ventricle and the pulmonary artery) is too small, narrow, or stiff.
Symptoms of pulmonary stenosis depend on how small the narrowing of the pulmonary valve is.
If symptoms are mild, pulmonary stenosis may never need any treatment. More severe pulmonary stenosis will need a procedure to fix the pulmonary valve so blood can flow properly through the body.
In children, pulmonary stenosis happens when a baby's heart doesn't develop the way it should during pregnancy.
Doctors don't know why this happens. It isn't caused by anything a mother did or didn't do during her pregnancy, so could not have been prevented.