Murphy224

Congratulations on the new baby! If I read your last post right, .. are the expectant mother and this is your first???
Ten years ago when my granddaughter came along, I made a lot of fitted flannel sheets for her crib. Found the directions online and used the very best quality flannel I could find. Flannel comes in an amazing variety of colors and designs now, not necessarily "nursery white, pink, blue, yellow". They held up very well and when she went to daycare about age 1, they used the foam mat type things for naps and each child had to bring their own sheet. The fitted flannel ones fit perfectly.
But you were asking about quilted fitted sheet. Mattress pads are quilted so that would work, but they are made of a solid piece of fabric. IMHO, A quilt with batting and backing made into a fitted crib sheet, would not be very practical. Crib sheets are subject to being washed daily and a lot of times with bleach and would be very hard on the quilt part of it. Save the quilts for tummy times, wraps when in a stroller, cuddling on the sofa, etc.