Pulmonary branches stenosis, also known as peripheral pulmonary stenosis refers to narrowing in one or several areas of the branches of the pulmonary arteries (blood vessels that carry blood from the heart to the lung). It may be a progressive condition, meaning symptoms can increase and become more obvious and disruptive over time. Many children with mild peripheral pulmonary stenosis do not show any apparent symptoms. Children with peripheral pulmonary stenosis are at risk of having insufficient oxygen within their blood, placing increased strain on the heart muscle. This makes the heart have to work harder. Peripheral pulmonary stenosis can affect each child differently, hence physician advice is recommended. Treatment often involves medication to work to re-dilate the blood vessels. Sometimes, peripheral pulmonary stenosis occurs as a complication of rare heart defects or certain genetic syndromes.