- In-utero the lungs are filled with fluid, the pulmonary vessels are constricted and oxygenation occurs at the placenta
- Oxygenated blood from the umbilical vein returns to the heart via the Portal circulation and via the ductus venosus that bypasses the liver to return directly to the Inferior Vena Cava
- Due to the high pulmonary pressures most blood bypasses the lungs via the Foramen Ovale or the Ductus Arteriosus
- In labour lung liquid production is decreased
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