We have adopted two children (two different home study agencies) and I do not recall any specific breeds of dog being specifically excluded.
Our dog wasn't a controversial breed (lab mix) but we were asked what we planned to do to prepare our dog for a child's arrival, how we would introduce her to the child, what we would do if the dog and child didn't get along, etc. Definitely be prepared to discuss safety issues with your social worker, but I would be surprised if there was a blanket exclusion (but I'm also confident that would be a question the adoption agency would be able to answer best specific to you situation, so I would call them if you are concerned.)