Sign Language for Autistic Children
Signing is one of the most natural and accessible communication supports for many autistic children. It requires no technology, no battery, no device, and is always available. For children who have the motor skills for signing, it can provide an immediate communication bridge, and a 2006 research review of AAC, including manual signs, found it did not reduce speech, with most participants making modest gains.

Types of Signing Used with Autistic Children
Does Signing Prevent Speech Development?
No. A 2006 research review of AAC interventions, mostly manual signs and picture systems, found that none of the participants in the strongest studies lost speech, and most made modest gains. When a child has a reliable way to communicate what they need, the pressure and frustration around speaking is reduced.