can my 12 month old sleep on her big sister's old mattress?

[SchrodingersSexKitten]

I know newborns have to have their own mattress (new) in a SIDS avoidance measure, but now DD2 is 12 months old and I am wondering if she can sleep on her big sister's (aged 3) mattress or if we need a completely new one?

I assume danger of SIDS has dissipated now, so passing on the mattress is OK?

I don't see why not. All of my children slept on the same mattresses, from birth.

Yes