That would be somewhat untrue even in the womb they can understand speech. God created the speech that people use. Coming out of the womb they can know who their mother is. To say that he absolutely doesn't understand the Created world would be false. He might not know as much as adults understand, but he still has enough understanding to condemn himself, Besides it the condemn heart that is tinted with Adam's sin that condemns us. Even so his sinful heart only cares about God's creation so far as it is to his advantage. The Babies viewpoint is that he is the center of the universe, of course it doesn't take him long to learn that if wants to get along in this universe he'll have to play by someone elses rules.