I think it's important to point out the "degrees" of childlessness. For instance, I know a couple who is not going to "try" to have children, but they don't like to call themselves "Childless by Choice" or whatever the women above are touting, because if they did happen to get pregnant, they would welcome "God's Little Surprise" and raise it whereas other "Childless by Choice" couples would go to ANY lengths--including abortion--to not have children.
You have raised a critical point. If we were to have an accident, so to speak, he or she would be our little blessing. We are starkly anti abortion even though we are still childless.