This sounds like a perverse incentive [0]. If you reward impoverished people for having children, it is not unlikely that the net result will simply be more children birthed into poverty.
The foster system is rife with perverse incentives, and Canada is experiencing a population decline. Is it actually a perverse incentive to raise more indigenous kids in stable homes with guaranteed income?
And, this touches on a broader conversation about UBI. IMO, payments for the kid should start in the third trimester. Our society does not value stay-at-home parents nearly enough. It's a job, and a damned hard one at that. Doesn't do much good to give people a guaranteed income that's too small to raise kids on -- you'll end up with parents working multiple jobs and the cycle of poverty continues.
I guess one option is to reward everyone for having children. Although this only makes sense if you want more children in your country. Some countries do. Singapore apparently has a giant "baby bonus" of incentives worth $121,400 USD to have 2 children.
I think it depends on your definition of poverty. If you define poverty as having an income below a certain amount, and you pay parents above that amount, then by definition the kids aren't born into poverty.
[0] https://en.wikipedia.org/wiki/Perverse_incentive