Few people are aware that May Eve, or Beltane Eve, is almost as spooky as Halloween. My trusty Perpetual Almanack of Folklore reminds us that it’s important to keep babies safe at this time:
A crust of salted bread under the baby’s pillow will keep off witches, but to be sure, hang garlic and rowan leaves round the cradle as well, and leave a bible among the bedclothes.
Though efficacious against baby-stealers, a knife jammed point upwards near the cradle is perhaps not to be recommended for babies…
I would agree with this last point. If your baby isn’t too restless you might try barbed wire or something, but in this day and age there’s probably some sort of electronic alarm that would defeat the snatchers almost as effectively.