What happens to the blood flow in a fetus when it is born?

When a fetus is born, significant physiological changes occur, particularly in circulation. Before birth, the fetal lungs are filled with fluid, and the placenta serves as the primary site for oxygen exchange. Blood is redirected away from the non-functioning lungs through structures like the ductus arteriosus and foramen ovale.

Upon birth, the baby takes its first breaths, leading to a major shift in circulation dynamics. As air fills the lungs, resistance in the pulmonary vasculature decreases, allowing more blood to flow into the lungs. This increased blood flow is crucial for the newborn's adaptation to breathing air, facilitating oxygenation of blood and the removal of carbon dioxide. Consequently, this shift supports the establishment of the newborn's independent respiratory and circulatory systems, highlighting the importance of increased blood flow to the lungs during this transition.

The other options do not accurately describe the changes in blood flow that occur at birth. Blood flow to the liver does not decrease; it often maintains or can even increase due to the need for metabolic functions. Blood flow to the brain remains relatively stable as it is critical for sustaining consciousness and neurological function. Furthermore, blood does not bypass the heart; rather, the heart takes on a more central role in circulating oxygenated blood