The countries that have the biggest financial incentives have very low birth rates. The poorest countries have extremely high birth rates. The poorest country in the world that doesn't even produce enough food to feed it's own people by a large margin also has the world's highest birthrate of about 7 children for every woman. For comparison most European countries and developed Asian countries are about 1.5.
But, Ukraine is also relatively poor and is still about 1.5. So it has a little bit more to do than that.
Mainly if you want people to have more children they need to be uneducated, poor, and the women need to not be working.
Or maybe they could just have pedophiles provide free child care as the cost of child care is what a lot of parents cite as a reason for not having another child. But, then again even in countriest, states, regions that have free child care it doesn't seem to work.