Ductus arteriosus

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The ductus arteriosus (DA) is a shunt in the circulatory system of the fetus during pregnancy. The DA is apparently maintained by low oxygen and prostaglandins in the fetus before birth (both are vasodilaters). Upon delivery, the newborn undergoes adaptation to extrauterine life, and the decreased pulmonary vascular resistance reverses blood flow through DA due to a strong smooth muscle contraction in the DA caused by oxygen-rich blood with less prostaglandins. With time, the connective tissue is closed anatomically by connective tissue growth.