My waters broke in bed in the middle of the night and it really wasn't a big deal. I got up right away and went to the toilet, but they definitely gushed out as I was lying down in bed. It was enough to make maybe a 1 ft in diameter wet spot on the sheets, but it really didn't soak through to the mattress that much. I would say it's not much more than the kind of wet spot you might leave on the bed doing other things, if you know what I mean, and it certainly smells nicer and seems less gross, I think. We changed the sheet, but didn't do anything special with the mattress. It was fine. If you are really concerned, you could put a bed mat (maternity kind or like a puppy pad), underneath the fitted sheet, to catch anything that might trickle through. Honestly, I wouldn't really bother though. I didn't think it was a big deal and it dried just fine.