Not sure what to do about this as we have ds's cot and mattress and we were going to use the cot for new baby but I have heard you need a new mattress? The problem is ds hardly slept in his cot (v clingy and co slept most of the time then went in a big bed at 2.5) and his mattress was a v expensive one so feel its a bit of a waste but obviously if I have to get a new one I will. Any advice?