How many babies who are born premature die?

I don't really know how many babies are premature but I have heard that most babies who are premature don't live which I think is real sad because usually the parent either smokes or drinks while they are carrying the baby in the womb. Another reason why I think it is sad is because the baby didn't ask to be born and when babies are first born they get messed with and then like when the babies are premature they already have to go through enough and then a few hours or days later they die or almost die that is not fair at all.