I believe it is higher. About a 3rd of kids in care in Australia have disabilities, and a huge amount of their parents have disabilities too. It's really a symptom of our lack of support for people who may be more likely to need some help, not their capacity to be parents, or the needs of the kids.

I really wish there was more research in the area. I asked a heap of professionals for resources for our little dude when he was born, but everything about adoptees with intellectual disabilities was for kids from orphanages, not local open adoptions. It was really fucked up.