There could be a number of reasons to baby loss during birth. The ones we see in movies are just plain stupid.
Sometime the baby does not get enough oxygen during birth, so it dies because of lack of oxygen. Sometimes, the labor gets too prolonged and can result in a dead baby.
At times the baby is already dead and no one knows about it so the delivery is of a still born baby. At times the lack of proper medical facilities can result in the death of the baby.
So you see there can be a number of causes and it can only be medically determined.
