My husband and I have 2 children together, and I have 1 son from a previous relationship long ago. I feel as if I was selfish a long time ago, because I really was not ready to be a mother at 18. At that time there was a lovely couple who had tried for a long time to have a child and couldn't. They would have taken him gladly, but I just could not do it, ready or not. That, in hindsight, seems selfish. Of course the 2 children my hubby and I have are well loved and supported by us. That does not feel so selfish.
So, really, it can be seen as selfish either way. I think people should not have children unless they are certain they can take the time to raise them properly and to love them fully. In my opinion, having children just to have them is selfish.