But, if you don't want to have kids, then you can give away your child units. This deals, I think, well with the issue of planned children. It allows people to have more that say two kids, but allows the community as a whole to prevent it self from growing faster than replacement rate. As you can see I'm a proponent of some sort of limits on children. Partly I feel this is symbolic.
Population is one of the problems in the world contribution to non-sustainabilty.
I feel that it's important to send the message of limiting your population as a community.