You can easily clean the entire surface of the mattress with soap and water thanks to the reinforced waterproof cover and lock - stitched waterproof binding. (followmum.com)
So, the inner surface of mattress is considered an ideal place for this. (shrewdmommy.com)
The patented waterproof surface of the mattress protects the interior from urine, spit - up, and other messes, and it's easy to wipe clean. (blog.guguguru.com)