Both parents have to work, if you want to increase birth rates then you can't force everyone to be a dual income family.
You'll notice that all the high birth rates are with single income family structures.
You'll notice that all the high birth rates are with single income family structures.
Clearly paternal leave doesn't fix the core problem since it's been there, and grown, over the entire time the birth rate has fallen.
It doesn't even make sense to do it unless both parents have exceptional careers, and most people just have mundane jobs.