I think that's confusing correlation and causation on childbirth there.
Other places in the world that do not require multiple exits for fires tend to have lower rates of fire death than we do in the US. The multiple exits thing is not actually for fire safety, it's to make multifamily housing harder to build and have less pleasant floor plans. Better fire suppression technology, having closer access to the stairs, are things that actually improve fire safety in practice.
People in cities have fewer children, and since children are the future tax base you might want that to occur so that you're not ground up into dogfood in your old age to pay down the national debt.
I do wonder how people think office buildings will comply with fire code which demands multiple avenues of escape from bedrooms during such a catastrophe.