A girlfriend and I both experienced this with our pregnancies. We were both told it was 'carpal tunnel' or an experience very similar. The solution I was told when I woke with the pins & needles was to raise the limb in the air and rotate the wrist. This seemed to get rid of it very quickly. It's now starting again for me this pregnancy, again when I sleep. I just do the same thing and haven't had any ongoing problems.

Cheers,