My mom had a piece of waterproof hospital sheeting (which you can also buy at Fabricland now) and that's under her sheets. She has quite the layers: waterproof sheeting, mattress cover/protector, which is just a queen-size flannel blanket folded in half, a undersheet and her top sheet. This way, no yucky, crinkly, sweaty plastic under her sheet. I was tempted to crawl in with her!
This is what I get when I tell her to smile.
My big girl! She's such a love!