At first I used the spiral tool:
This looked pretty unspectacular. I've seen it before, so I tried something else that really got me thinking:
The twist tool can be made to create unpredictable objects, but with a certain degree of control. This was made from a full circle, which created an interesting spiral shape. I attempted some more below, having more control this time to shape it into something that I wanted.
I love the middle one. I just love how it still has a solid shape, and in a way it looks like a fetus, which is incredibly relevant. The only trouble is, it looks a little ropey at the moment. This is the process I took to restore the shape back into a circular, smooth, shape.
I did this by simplifying the shape: