Around the 3 month stage, (2 months out of the hospital....) I noticed that Emily's motor development wasn't where I thought it should be. I had her evaluated by our county's birth-to-3 program (similar to what Liza mentioned, I'm sure). They were great. She was evaluated by an educator AND a physical therapist. We started on a Physical Therapy program because they agreed that she was slightly behind. The PT had a theory that some of the lack of devleopment was due to discomfort from reflux. As the reflux improved (with medication), and with therapy, the skills began to develop. She was walking just after her first birthday.
My other theory was that the first month, spent in a hospital, hooked up to monitors and wires...was not conducive to normalmuscle development. She caught up, by any means.
Look into what your county/school district offers (I know it seems ridiculous to think about the discrict for a 10 month old...but they usually have 0-3 programs...) and at least do an eval. that way you'll have an opinion and you can move on from there. He'll catch up in the enc, but it would be nice to cross one thing off your "Worry List" a bit sooner.
Good Luck!