I have to politely disagree. The places that have highest fertility rates are places where contraception is hard to obtain and may be outright banned, and where womens' rights are severely restricted. That is, closer to nature, not far from other mammals. Such societies also usually have high levels of infant mortality, making bonds between parents and infants weaker.

This is not a society most of us want to return to.

I'm afraid that the only realistic way is "elvification" of sorts: make adults live, stay healthy, and remain productive for much longer to eventually compensate for very low birth rates, and the very high cost (not just monetary) of raising a child.