I suppose the previous status quo that anti-natalists want to return to is before the evolution of intelligent life. Word is still out on whether it's immoral for single-celled organisms to reproduce.
I'm taking an utilitarian approach. Suffering should be avoided, and happiness maximized. Bringing another being into existence guarantees suffering, with a chance of creating happiness. That is not a gamble you should take on behalf of another being.
Is the potential (or guarantee) for suffering greater than the potential for joy? You also have to account for the joy of the person and the joy they create. I believe the potential for expected joy exceeds the guarantee of suffering.