It’s probably not a “want” as much as it is an economic decision.
Your highest birth rates are in developing, backwards countries. It has long been accepted that the reason for that is that in those countries, your children are a financial asset; they work in your field or your shop, and when they are grown, they become your retirement insurance.
As countries develop, and as social infrastructures are built, children move from “asset” to “liability” in the financial sense. The child does not have a return on investment, since they don’t work at your job as free labor, and they are no longer needed as retirement insurance.
So, the more expensive higher education gets……… (more generally, the more expensive it becomes to raise a child to adulthood, the more the birth rate is depressed.)