Is there any validity to the folk tale of cats smothering infants? I can see where there might be a risk to a toddler or infant whose reflexive defenses might be too feeble to push or awaken a fat sleeping cat.
I’d say “No”:
http://www.snopes.com/critters/wild/catsuck.htm
(Note that this starts with the “Cat sucking the breath out of a baby” story but also discusses the “Kitty accidentally smothering child” bit)
I’ve got plenty of friends and family who raised babies with a variety of cats in the house and nobody’s died yet. The worst I’ve seen is a scratch which is often how kids learn not to yank on kitty’s tail.
If you want to back a little further, toxoplasmosis can cause a miscarriage and can be transmitted when a pregnant woman cleans cat litterboxes. My mother miscarried what would have been a younger sibling at 6 months because we had 5 cats at the time and she took care of them.
I hate to open up this can of worms again, but here’s Cecil’s take on the subject: http://www.straightdope.com/classics/a4_081.html
In other words, it’s not inconceivable a cat might sit on the respiratory apertures of an infant or enfeebled person and cause hypoxia.
Remember, violent dissent should go to the pit, just like the last time we did this. 
no no no… it’s minature Trolls who live in the wall who suck the breath from babies. Cat’s are the Heroic Defenders who keep the Trolls at bay!
Didn’t you ever see Cat’s Eye?