Which change is a normal physiological event after birth regarding the heart's circulation?

• A. Closure of the ductus arteriosus and a shift of blood flow through the heart
• B. Ductus arteriosus remains open
• C. Blood flow reversal in the aorta
• D. No change in circulation

Answer: (A)

After birth, the heart undergoes a transition from fetal to neonatal circulation. The ductus arteriosus, which in fetal life bypasses the lungs by shunting blood from the pulmonary artery to the aorta, constricts and closes once the lungs expand and oxygen levels rise. This diverts blood to the lungs for oxygenation and allows the left heart to pump oxygenated blood to the body while the right heart sends blood to the lungs. Closure is driven by increased arterial oxygen tension and a fall in prostaglandins after birth, and it becomes permanent over time. Persistent openness of the ductus arteriosus, reversal of blood flow in the aorta, or no change would not reflect normal newborn adaptation.