Which of the following would be more fair?

The fist one would be extremely fair but un-enforceable.

The second option is what we got and it spells doom.

Your question is insulting to the many people who grew up in poverty where money was hard to come by, and they struggled got by as best they could, helped each other to make ends meet and live happy lives. You have very inhumane viewpoint i must say if you are actually considering that first one as a viable option.

I'm assuming you aren't talking about third world countries ? ' poor' is vague. even so, it's an absurd question...

There are, and have been many large families who lived in poor conditions, who get by, and are happy.

you make the assumption happiness, and a nice life depends on financial wealth and materialist goods, and that if a child grows up in a home where they haven't many material riches, that theres is a life of not much worth . That's disgraceful .

and how you would you go about enforcing such a barbaric law?

The option that is not taking the responsibility away from them and forcing an invasive medical procedure on those who do not need it.

Not to mention having a government decide who can and cannot have a child is pretty scary.

Poverty children did not make.and they don't bring it with them but the society that is not fair to spread the Common Wealth equally and justly.

This isn't you diary.