Just because it is a biological prerogative does not mean that it doesn't cause suffering. I've seen lions eat gazelle babies straight out of the womb, is that not suffering? Now, that is an extreme example, but people having kids in a bad environment, just because they can, can cause undue suffering to the child. That is why it is prudent to wait for the right time, is the parent commentor's point I believe.

There's an incredibly wide range of "bad environment" - where's the line (and who decides where it is)? Should only people living in the first world get to have children?