Other parents have blamed themselves for things like prescribed medications or illnesses that caused prenatal damage, accidents where their children were seriously injured, being unaware of a hereditary condition in their family, etc.
While some disabilities are the direct result of choices made by the parents, in other cases there was no way anyone could have predicted the outcome. But often, even when parents couldn't have done anything to prevent their children from having disabilities, they feel guilty about them.
But it doesn't matter if the parents were responsible or not, living with guilt makes it more difficult for them to meet the needs of their children, and parenting kids with special needs is difficult enough without that.
When I worked in the dormitories at the California School for the Deaf I noticed that nearly all hearing parents had gotten divorced by the time their children were in their teens. Of course some of them probably would have done that anyway, but other marriages couldn't handle the stress of having kids they considered disabled. However the deaf parents considered their kids perfectly normal, so that stress didn't exist in their families and most of them stayed together.
Fortunately many more resources to help families deal with disabilities exist than used to be available and I hope most parents take advantage of them. And if they feel guilty, for the sake of their children and their marriages, I hope they'll get counseling and learn to forgive themselves.