My 3m baby Not turning head toward sound

Developmental milestones are checked according to corrected age and not actual (chronological) age. If your baby was delivered at 33+4 weeks GA and chronological age is 3 months, corrected age would be around 7 weeks or about 2 months. For this age, smiling, making cooing sounds is good. Baby would also show a startle reflex when exposed to sudden loud noise. Turning the head towards sound develops by around 3-4 months, so no need for worry right now. However it is important to get regular neurodevelopmental follow ups for preterm babies, as the risk of delay in milestones is higher for preemies. Also a hearing screening test is advised, ideally within the first month of life. Test is called AABR test and it is a standard protocol to get it done before discharge from the hospital, especially if the baby has stayed in NICU. You can contact your pediatrician for the same.