well, let's see,
I've walked under ladders, and broke mirrors, and stepped on cracks, and opened umbrellas in houses, so those myths are all debunked.
I've heard about cats "stealing" babies breath before.........that goes back to olden days when people believed in vampires. Vampires could transform themselves not only into bats, but cats as well. Cats naturally like warmth, and baby cribs are filled with stuffed animals, pillows, blankets, and cats would snuggle in to get warm, and I suppose a few babies were accidentally smothered in the process. Between that and the vampire lore, that's where that story came from.