Human Growth and Development

Prenatal Developmentfetal Stage

How does the fetal circulatory system change at birth?

Immediately after birth, an infant no longer relies on maternal blood to supply oxygen and nutrients. As soon as the baby begins to breathe air, blood is sent to the lungs to be oxygenated. The ductus arteriosus, the special fetal vessel connecting the aorta and pulmonary valve, is no longer needed and closes. A separate left pulmonary artery and aorta form after birth. In addition, the foramen ovale, the special opening between the left and right atria in the heart, closes and normal circulation begins.


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