Why does the blood of an unborn baby bypass lungs until after birth?

The blood of an unborn baby bypasses the lungs until after birth because the lungs are not fully developed and are not yet capable of gas exchange. The baby receives oxygen and nutrients from the mother's blood through the placenta.

The placenta is an organ that grows on the wall of the uterus during pregnancy. It is connected to the baby by the umbilical cord. The umbilical cord contains three blood vessels: two arteries and one vein. The arteries carry deoxygenated blood from the baby to the placenta. The vein carries oxygenated blood and nutrients from the placenta to the baby.

The placenta acts as a filter for the baby's blood. It removes waste products and carbon dioxide from the baby's blood and provides oxygen and nutrients. The placenta also produces hormones that help to maintain the pregnancy.

After birth, the baby's lungs begin to function and the baby takes its first breath. The blood vessels in the lungs open up and the baby begins to exchange oxygen and carbon dioxide with the air. The placenta is no longer needed and it is expelled from the body.