Does learning a sign language interfere with or help, hearing and deaf children learn a spoken language?
There is no research evidence that learning to sign interferes with deaf children’s spoken language development. On the contrary it may assist children learn difficult to understand concepts and act as a bridge to learning these words in spoken language.
Signing with hearing babies is a fun way to get to know your child, in the same way reading books or singing nursery rhymes is always going to be beneficial. There is no evidence that hearing babies have faster language or cognitive development than other groups who do ‘child-centered activities such as nursery rhymes. The following link has more information of research centred responses to this question.