My DD didn't crawl till 13 months and didn't bear weight on her legs till about 11 months. Even then she didn't really like doing it - was more consistent around 15 months when she atrted standing. We were never overly worried or referred to anyone. She walked at 19 months and now you would never know that she was a late develper - physically. Some kids just take longer and I honeslt y think some of the "timelines" in books are way small.