No, they are listed as examples of severe disabilities in their own right. There's a list upthread, I've pasted it below:
*In one study of 241 children born before 26 weeks' gestation the following was found (9):
22% had severe disability (e.g. cerebral palsy and not walking, low cognitive scores, blindness, profound deafness)
24% had moderate disability (e.g. cerebral palsy and walking, IQ/cognitive scores in the special needs range, lesser degree of visual or hearing impairment)
34% had mild disability (defined as low
IQ/cognitive score, squint, requiring glasses)
20% had no problems*
I've read this before, and it was clear those were examples of what is meant by severe, moderate etc, not that it only applied where they occurred together. So, for example, Fury (TV Gladiator, deafness caused by prematurity), would be counted as 'severely disabled'.
The stats need breaking down.
The question that is in most people's minds realistically, when they hear the chance of a child born with a severe disability, is whether their child will have a good quality of life, will they be able to live independently etc. I'm not sure they current categories of disability actually let people assess that.