There are high pressures in the fetal lungs causing decreased pulmonary circulation.

Blood shunts from left to right in the fetal circulation.

The ductus venosus allows freshly oxygenated blood to go to the fetal brain first.

There are higher pressures in the right atrium in the fetal circulation.

After birth, the fetal circulation system undergoes significant changes as the baby begins to breathe and the lungs become functional.