I think you should be careful about how you word this. There are many couples who are unable to have children through no fault of their own. For some reason, known only to God, He has decided to withhold natural childbirth from them. By the same token, not every reason that people use to decide not to have children is selfish.
Reading back I could see the mistake I made. Children are a blessing from God. He chooses who He will bestow this blessing upon and when. Having or not having children is not an indication of worth. My comment was merely that there is never a reason for us to tell God, we don't want that blessing.
However, I still stand by my original comment. In a world of perfect faith, it is always selfish to decide not to have children if God gives you the ability. I'm open to suggestions why it's not but I'm pretty sure they can all be traced back to selfish reasons. (medical problems is a difficult area because God gave us doctors to help us with our health and brains to make good decisions but also faith to trust that ALL things work for good to them that love the Lord)
It is however permissible if people choose to not have children for a multitude of reasons, but that's not the question.
Again, my personal opinion and belief has been stated above. I'm open to discussion about it but when we thwart God's gifts we always pass up blessings. However, I think every Christian (who believes life begins at conception) should agree upon the means used to prevent those children. Some are clearly against God because they destroy a fertilized egg by preventing it from implanting and growing further.