Does any one know the risk of mental retardation if born to soon after gastric byp?

My ten year old son was developmentally delayed across the board and still has some small issues. He didnt sit up to well over a year crawl around 18 months and walk around 2. Other than some small issues he is a typical 10 year old boy. He wasn't grabbing either. You can call in early intervention to start working her that is what i did. She might be doing everything at her own pace. Don't worry about anything just yet. hope i helped