Obviously to remain immortal you must not have child. Once you decide to make one, your immortality is forfeited. I think it would be a great achievement
Basically this, having a child is a way for some part of you to remain when you leave the world, I think in a world where immortality is possible you will need to give up your rights to have kids, and if you want to have kids then you will forfeit your right for immortality.I would agree to such terms. Although not sure if I want to immortality. Probably it is very boring. It would be nice to immortal man had a chance to die.