My Son is going to be 4yrs old but cannot speak. Only he utters few works like baba , mumma somethimes.?

Possibly mild form of Autism or deaf. You should have him checked out.

Im not sure how you are around him, but one thing I would suggest is to talk to him as you would someone much older. I never really did baby talk with my son, I always got to eye level with him and just spoke normally. But I dont think its much to worry about being that kids develop at different rates. As long as you have done test to make sure it has nothing to do with his hearing, just start speaking to him normally, and dont try and force it.

Take him to a pediatric clinic or a pediatric neurologist for an exam and testing. There is something not right here but you will not get the answers from a bunch of Yahoos. Why did you wait so long?

I would definitely consult a speech therapist and the child's Dr. He could have some sort of hearing problem or maybe hes just very delayed due to the prematurity. I would be worried by this point that there is no change. he should be able to speak a full sentence by now.

Talk to your doctor or a health proffessional about your concerns he may just be lazy with his speaking if he points to something wanting you ti guve him it tell him he can not get it until he says what it is. Good luck

This is most likely natural , some people learn at different rates . continue to show him words ( and say them ) . show him how to spell his name ( like with blocks) . he will get there

he is deaf

He should be fine. I was born prematurely and I didn't start talking until I was three. And I've been talking ever since.