Is it ok to use a thin cotton towel as a mattress protector in a bassinet, underneath a fitted sheet? If yes, does the towel need to completely tuck in around all sides of the mattress, or is it ok to use a towel that tucks in on both long sides but isn't quite long enough to tuck in at top and bottom of mattress?
Red Nose recommends the following for mattress protectors.
Ensure the mattress is a tight fit and does not compromise the firmness of the mattress.
From the Red Nose website in relation to “What is a Safe Mattress?”:
Always make sure that the waterproof mattress protector is strong and a tight fit. Never put soft bedding under the bottom sheet.