My mom used them, well, vinyl ones, for my brother Ger in the 80s. He was a very deep sleeper, so he was incapable of waking on his own to pee at night until he was about 5 years old.
They seemed to work fine. We also had vinyl mattress protectors (zippered around the entire mattress) plus mattress pads & sheets, just in case.
However, for me, I'd get wool wraps or pull-ons. Of course, that's what I used with my DD for nighttime cloth diapers, so I already have a few covers.
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Liz
DD (3/2010)
"Make mistakes! Get messy!" - Miss Frizzle