Children are public goods with massive positive externalities. I think it would be a shame if the population declined.

My favourite policy to increase birth rates is to give parents a percentage of their children's income tax revenue. Standard econ says we just need to internalize some of these positive externalities. This has the advantage of scaling with the wealth of the parents, as economic productivity has a significant heritable component.

Though this policy triggers an intense moral disgust response in everyone I've proposed it to, so likely not possible unless things get very desperate. But I think it has a chance of working, which is more than I can say of most natalist policies I have seen.