I am expecting baby number seven so I have something to compare it too. Baby number three was crazy active in the womb. I could have sworn he had 8 arms and 8 legs! By nine months old he was not only walking, he was running and climbing. His physical abilities surpassed his cognitive abilities so he would often put himself into dangerous situations. He has participated in and excelled in multiple sports. He started speech therapy in kindergarten, and became eligible for an IEP under specific learning disabilities (dyslexic) in second grade. When he was 10 he was diagnosed with ADHD and sensory processing disorder. When he was 12 he received the additional diagnoses PDD-NOS and anxiety disorder. I strongly feel that the hyper activity and the sensory seeking were noticeable in the womb due to him being such an active fetus.
My DS with hypotonia wasn't very active as a fetus and he is more laid back with a chill personalty. Due to his low-tone he didn't sit up by himself until he was 9 months old and he couldn't walk until he was 18 months. He has a severe articulation disorder that is partially due to low-tone with regard to oral motor. He also has learning disabilities and sensory issues but likes passive input as opposed to his brother needing active input. This all makes sense to me since he didn't move much as a fetus.
The four other children were what I considered to be average fetuses with typical movement. They have met all developmental and academic milestones on time or early but not early like reading at two years old or anything astounding.
I have no idea if there have been any studies relating fetal activity and childhood traits but it would be interesting.