Okay, are the wave-like movements the kittens just moving in the uterus or is it the kittens moving down toward the birth canal? The kittens seem to moving a lot.

You will not see the kittens move toward the birth canal, the movement to the will be so gradualyou will not see it . The waves of movement you are seeing is the kittens themselves moving around.

http://www.petfinder.com/journal/graphics/gp3.jpg