Baby Mattresses And Waterproof Protection

What ever mattress you buy try and ensure it has:-

 1) Waterproof Protection
 2) Breathable machine washable cover
4) Excellent supportive base that will not dip nor dent

Waterproof protection can either be:-

1) Over the top of the mattress
2) Under the mattress cover but over the mattress core

If the waterproof protector is over the mattress cover it will  protect the mattress but your baby will be lying on a protector that is not fully breathable.  

If the waterproof protector is under the cover it will still protect the mattress core    but your baby is lying on a comfortable machine washable breathable cover

If the mattress cover has special properties like Coolmax & Maxispace then these features become ineffective if covered with a protector. Put the protector under the cover

If the mattress cover gets soiled because the urine goes through the cotton sheet  you can just wash the cover.  Urine will not get to the core because the mattress protector is under the cover.

Natural or Synthetic Covers

Natural 100% cotton covers are not waterproof. 

Outlux is 92% cotton fabric with a waterproof  PU centre  but it is only very  slightly breathable as nothing gets through the PU layer in the middle of the fabric.
Synthetic covers like Coolmax & Maxispace and mIcrofibre toppers are  fully breathable and machine was well but not waterproof. They zip on to an easychange waterproof protector that is wipe clean.

Playing devils advocate -If you put a cotton sheet over a Coolmax & Maxispace  mattress cover your baby is virtually the same distance from a synthetic fabric as it is if you put a cotton sheet over an Outlux fabric, because the centre of the Outlux is PU,