My girls were born at 28 weeks, with my smallest weighing only 1 lb. 15 oz. She was considered IUGR. Actually, they had been watching her growth from about 7 weeks gestation, because she was showing up small at that point. At 1 yr. she weighed about 16 lbs. (can't remember exactly - they just turned 5) but I know my pediatrician never worried too much about her growth, as long as it was steady over time. She is still my smallest one, weighing only 31 lbs. at 5 yrs. old and finally just making onto the growth chart for the very first time but that could be genetics as much as anything else. Although my husband and I are average, both of our parents are on the small side. Although she had a lot of therapy, that really had to do with the extreme prematurity and not the size. She's an absolute dynamo now. My theory has always been that considering how premature she was if the worst thing in life she has to confront on a long term basis is being petite then life is good. I would be aware of your son's growth to make sure he is making his own growth curve (whether or not it's on the official charts) and try not to worry too much beyond that - easier said than done, of course. And Happy Birthday to your guys!