When my daughter went in for surgery to have her gtube installed when she was 3 we did see quite a lot of regression, but the surgery was in the midst of a lot of medical trauma. She has a white blood cell disorder as well as autism and the other condition was causing her a lot of pain. Once the she healed and got used to the gtube however, the relief from pain was visible and everything has gone so much better since then. So even though it was hard getting through those months leading up to the surgery and the surgery itself, taking care of the medical issues so she is comfortable and happy has made her progress in her ABA therapy and school now so much better.