Dr. Jon,
My mother always thought that the idea of cats stealing baby's breath was really a matter of cats licking a bit of milk or other food from the baby's face after the baby ate; that's why the cat was close to the baby's face and even mouth, and could appear to be stealing its breath.
As for cats being in the baby's cradle, I always attributed that to cats liking warm, cozy places. And I've also always believed that cats like to sleep so much, when they see someone else asleep, it's just too tempting situation not to join in! Therefore, cats and babies are a natural combination!
