I think this is where a lot of modern civilization is falling apart at. If you want population replacement and growth, you actually have to make it advantageous to have children, and at appropriate age for your society and culture. The GOP thinks they can do it by destroying reproductive rights, civil rights, and marriage laws, if they harm women enough they'll HAVE to be baby makers! Dehumanized baby factories! And even conservative voters are fighting against it, because it's insane and it's against our current culture. It has to work for everyone. It would be more intelligent to create free childcare, better pregnancy and birth leave for both parents, and child tax credits. They could use WIC to absorb the cost of having a child and public education sooner with preschool. If people are hopeful their children will have high education access and a stable life they will be a lot more likely to have kids. Being horrified that your children will live in a fascist theocracy and intentionally kept uneducated and poverty stricken, they might actually voluntarily avoid sex to not have kids.