Dear ?
I will attach some information about "normal development" and motor systems.
If you really want to learn more about normal and variablility in motor development I suggest you have a look at the following site.
Karen E. Adolph > Home
This young professor has researched so much on motor development. Prepare to need some time... She has written so many articles. One on the cultural differences in motor development is especially interesting and to the point regarding your question.
The best advice I can give you is facilitate the child, and wait, give him/her time to react. Do not make the mistake of not waiting long enough and passively assisting.
We now know that most prematurely born children are slower in reaching their developmental milestones.
good luck
Esther