Why do babies cry immediately after birth

"The cry of the baby serves as a strong respiratory effort, thereby aiding the baby in his first breath "

 

When the baby is still a fetus, the baby does not breath using his lungs. Instead, oxygenated blood from the mother flows to the placenta where nutrients and oxygen are exchanged with the baby's blood. During fetal life the baby's lungs are filled with fluid and they do not perform any respiratory functions. During this time the baby's lungs remain collapsed. However at birth the placental supply of oxygen and nutrients are cut off, as a result of which the baby is forced to breathe on his own. At this point the lungs expands and the baby starts breathing on his own. 

The cry of the baby serves as a strong respiratory effort, thereby aiding the baby in its first breadth. However before the first breath, the lungs of the baby is still filled with fluids and considerable force is required to inflate the lungs for the first time. Once the baby starts breathing, the fluids are extruded out through the nose and mouth and usually suctioned to clear off the fluid from the lungs.

Another possible reason why babies cry could be that, they are bruised and sore from the trauma of birth. And usually the process of birth is so exhausting to the baby that a newborn baby will sleep for the next eight hours or more. Till recently, babies who did not cry where stimulated to cry by holding by his legs and spanking his bottom. However this procedure is not usually followed anymore as its considered not necessary anymore.

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