You're wrong to have it enforced, the one child policy had disasterous consequences in China for example. Not having kids is a consequence of a country being developed and educated.
The root cause is not having children, it is living in an agrarian under-urbanised society.
The tragectory is usually like this:
Parents who work on the farm have lots of kids to help them farm, most of them died because of diseases.
Once a country has access to energy, then we can use fewer hands for farming.
People start migrating to cities.
Only the first generation of migrants have lots of kids.
The 2nd generation usually realises how expensive life costs is than have fewer kids.
What Africa is experiencing now is the first migration, all predictions is that the world population won't ever reach 11 billion people and by the end of this century most Africans will life in cities.
Essentially a population boom is part of a country's development. It is as sign of increasing wealth and prosperity, not the other way around.