He/she will probably be quite a bit behind schedule with some things--especially speech and walking, but they still make progress and may catch up later.
Catherine Zeta Jones was a trachea/vent baby!!! One of my fellow nurses was a trachea/vent baby!!!
However, it is downright mean not to level with the parents of a premature baby that is 18 months old and who is not grasping and playing with toys, interacting with people, and trying to sit or stand.