When should you start to worry about speech development?
DD is 20 months and has been having babble conversations (where she really seems to be talking to you but only makes sounds) since about 11 months and has been saying mama (for any person) and ba (for bye) for ages but has absolutely no 'proper' words apart from that.
She understands well, if you tell her to get her teddy, give you a hug etc she knows what to do but she can't speak.