During the 1970's, there was a social movement called "Zero Population Growth.” The idea was that people who wanted children should only procreate enough to replace themselves; in other words, two children per family. It was commonly known as ZPG.
For some reason this movement just died out. For religious or other reasons, people kept having kids and more kids, thinking (I guess) that, as long as they could afford them, why not? Personally, I feel that's taking the short view. There are other things to consider when it comes to planet population. There are ecological factors, health issues, loss of animal habitat. This latter one is a big deal to me.
When we first bought the property on which we live, we saw evidence of deer. We recognized where they bedded down and occasionally saw them peeking through the trees. After a few months of zealously crashing through the woods on the tractor, we managed to run them off. I've always regretted that.