Cot mattress - did you buy a new one for second child?

[CMac]

Just that really. I would buy a new one without thinking if i'd inherited a cot from another family but am not sure if it's necessary when it's just being passed down from an older sibling. Does anyone know the science behind the recommendation that you change mattresses between users - is it something to do with SIDS?

This is the official advice from the sids website:

What kind of mattress should I use?

It is very important that your baby?s mattress is kept clean and dry. Ideally you should buy a new mattress for each new baby. If you are not able to do this, use the one you have as long as it was made with a completely waterproof cover (eg PVC) and has no tears, cracks or holes. Clean it thoroughly and dry it. Check that the mattress is in good condition, doesn't sag, is firm, not soft and fits the cot without any gaps. 'Ventilated' mattresses (with holes) are not recommended as it is not possible to keep the inside clean.

DD didn't get a new one.

Definitely not. Cleaned it & aired it. I think if my first had been a very sicky baby & the mattress was heavily puked on then I might have considered buying a new one.
As I understand it, the danger comes from bacteria in baby puke.

Well I had just made my mind up and was happy using the same mattress dd used till I read Seona1973's post. Checked the SIDS website and it does say ideally you should use a new matress. Then again as SenoraPostrophe pointed out it's not one of the things they suggest you do to reduce cotdeath so is presumably not thought to be that important... The mattress is in extremely good nick as far as I remember and has never been in the attic or anything so i think i'll just go ahead and use it. Thanks for advice everyone.