One wonderful thing about Fuan no Tane is that the stories are so open to interpretation. Even in the most "complete"-seeming stories, quite a lot is left up to our imagination. Depending on how you want to read them, that can make the stories a lot scarier than they otherwise would be. Or, as I often prefer to do, you can just as easily imagine the scenario devolving into an amusing farce, instead.
So I would certainly agree that you could read the Big-Teeth Baby story as sad rather than scary. With this story, however, I tend to see it the other way. All joking aside I always figured that the "baby" is actually some kind of nurse-eating demon or something, a monster that wants to maul you with its giant teeth but that, like a vampire trying to get into your house, it needs an "invitation" before it can actually touch you.