This problem is directly connected to the true nature of the "wage gap". Women make less than men, not because they're paid less for the same work, but as a result of restricted career choices shaped by having and raising children. Where the wage gap shrinks, so does fertility. Wealthy, educated women are not going to have many kids, because it doesn't pay.

We need to recognize that raising children is vital but largely unpaid work and that this is unfair to women. Raising the next generation is a section of our economy that's not even recognized as productive labor even though everything else depends on it.

A stable society needs educated people to have kids. If you want middle-class women to have children you'd better start paying them for it like any other career.