Waters breaking or not is really dependant on the position of the baby. Mine broke with the twins (well twin I's waters broke) when I was at home. I actually got out of bed seconds beforehand because I could feel something happening - instinctive maybe to save the mattress? There was a lot of fluid though, so a waterproof mattress protector may be a good investment. I got a single one for $5 from kmart so something like that will protect your bed if your waters do break.