Does not reach for things

My son will be 6 months in 11 days, but does not reach for things. He was 4 weeks early and spent 2 weeks in Intensive Care Unit. I think he is progressing fine, but when I look at him and compare him to others his age, he is DEFINITELY not on their page.

Most other same age kids are reaching for things and bringing them towards them, grasping onto objects with a good degree of control, and maneuvering themselves using any combination of hands, legs, rolls, 1/2 crawls, etc.

My son just stares at toys in front of him, with no desire or ability to reach for them. Anyone else's baby behind in this? I guess the skill would be called 'willful movement.'