Check out http://www.babesafe.com – there is extensive research that shows cot deaths are more common on 2nd hand mattresses. In addition to buying a safe new mattress, You could also get a mattress cover from them which will keep your baby safe from harmful substances which may be present in certain mattresses.
I had a cousin who died from cot death so we are very aware of it in my family and I have always wrapped my mattresses with Babesafe covers for my 3 children
It’s a non profit organisation and the guy who founded it has been awarded an OBE for his work,
I had a spring mattress for ds1 he used if for 3 years, I chucked it in the bin and paid 125 for a new spring mattress then only to be told by the girl in the shop that its okay to use a spring mattress for 2nd babies etc…. I was a bit peed off that I chucked the mattress before I went shopping but then I had a think about it and God forbid the "What if’s?" started….. What if something did happen to ds2 (touch wood it never happens) but if it did I couldnt live with myself and would always blame myself, but if something did happen or if you thought you could prevent it you would ….. so in my eyes it was 125 euro well spent.
Cant understand how people would buy secondhand mattresses