My ds is 6 months next week (4 months corrected) and hasn't attempted any sounds other than ooooh. Just wondered around what ago babys usually start with the other sounds. If I do then to him, he just smiles!
DD (34 weeker) didn't have any other sounds at that age either. I think she did ga sounds from about 6 months corrected then dada from about 7 corrected and then mama and nana and occasionally ba and a few other more indeterminate sounds at 8-9 months corrected.
My ds1 Born at 26 weeks didn't really make any discernible noise until 14 Months and has a diagnosed speech delay. Ds2 Born at 24 weeks is now 9 months and makes a lot of noises some getting towards sounds. I think it really does depend button you're worried I'd ask your hv or gp x
My son was born at 31 weeks. He said his first word, mama, at 23 months. He's now 2.7yrs old and is saying at least 10 words and copying everything we say. All the Doctors have told me he'll get there in the end. He had a hearing test last Nov' to make sure there wasn't any other reason for his speech delay but it all came back normal, so it was just a case of him being prem and taking his time catching up.