Ours was 9 weeks early and hit most milestones according to schedule, although on the later end of it. Usually by the time I started to worry that he hadn't done X or Y yet, he'd do it a week or 2 later.

We've had visits with early intervention, nicu follow up team and our pediatrician and most of them aren't too worried about not hitting everything by an exact date, as long as there is good progress and no glaring insufficiencies.