Does a 20 week old need a new mattress when he moves into a cot?

[beansprout]

I have ds1's old mattress but wondered if I need to buy a new one for ds2 who is now 20 weeks.

I used dd's old mattress for ds (she had used it for about 12 months and it was still in good condition). The official advice from the sids website is this:

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 and has no tears, cracks or holes. Clean and dry it thoroughly. Check that the mattress is in good condition; is firm, not soft; fits the cot without any gaps; and doesn?t sag. Never sleep your baby on a pillow, cushion, bean bag or waterbed.

Thank you. I am not going to take any chances (we lost a neice to SIDS) so am going to play it safe and get a new one.