Having children is a human right and we don't have the right to deny someone the chance to have kids. Growing up in poverty does not mean growing up in a bad situation. Often the kids in slums are happier as they are grateful for everything they have and not totally spoiled.
Procreation's FEASIBILITY not ABILITY depends from income. Poor people ARE able to have children. Therfore it is not the question if they should or not. They CAN. And because they have no Plasma TV and cannot afford drugs they have more children than the rich. Or are poor countries underpopulated?
Although I think it's wrong to deprive someone of the choice to have children or not, I think that having children when you personally cannot live off of your own income is irresponsible; if you cannot live off of that income by yourself, what makes you think that it will get better when you have a kid? If anything, it allows for more people to become dependent on government assistance due to the fact that they now need to take care of a child, which is incredibly costly.