Sure, but if you were to poll everyone on if they were happy to be born, it'd be overwhelmingly yes. Your odds are pretty good of having a kid that was happy that you doinked.
But if, as hotpotamus suggests, "consent" is a useful way to look at this, then that's not good enough. You can't randomly do surgery on people just because you believe there's a 90% chance they'll be happy with the results.
There'd be a lot fewer people, otherwise. From a pragmatic point of view, we've likely evolved to answer yes to that question, otherwise we would've been outcompeted by another species with a thirst to live and reproduce.
Not necessarily, there are a lot of species that are functional no-ops, such as the Luna moths that grow up to be unable to eat anything as they have no mouths. They can only procreate, continuing the cycle. They are no-ops because there is nothing they can do besides procreate, they cannot even obtain sustenance. So, they might say that it was not worth being born, had they been able to be polled.
If you polled me, the answer would be no. I'm not exactly unhappy about it either, but I'm conflicted enough about it that it's not something I will do to another.
But if, as hotpotamus suggests, "consent" is a useful way to look at this, then that's not good enough. You can't randomly do surgery on people just because you believe there's a 90% chance they'll be happy with the results.