Answer:
Child mortality rates or industrial workers
Step-by-step explanation:
If children die young the parents will have lots of children to counter the children that die. so the parents might have 7 children to make up for the fact 4 might die if there is no hospitals to make sure the children live till adulthood.
morden or industrial countries less people want to have children as they want to follow there dreams so this will slow down the birth rate.