Question

How does the blood pump when any new baby is born? Does it flows through aorta first or the capillaries are filled with blood and pump starts?

Answer 1

After birth, the ductus closes and a separate left pulmonary artery and aorta form.

The fetal heart also has an opening between the upper chambers (the right and left atria) called the foramen ovale. It lets blood flow directly from the right atrium to the left atrium during fetal development, but closes after birth. So the ductus arteriosus and the foramen ovale are part of the fetal circulatory system before birth but disappear soon after birth.