My daughter was born a month premature at 3 lbs 15 oz. She just turned 10 months old and she still cannot sit up or crawl. I would be worried about her development, except that she is on track with her weight, she can say "dada" and hold her own bottle while feeding. She's very alert and more often than not responds to her own name. She doesn't have any gas issues, as she burps or passes gas pretty regularly when feeding. She has her first two teeth already, which I don't know is of any relevance or not. When she is put on her belly, she can lift her head up and look around for several moments and she'll even begin to push herself forward, but usually ends up either rolling over or rotating herself. Should I be seriously concerned at this point?