Thanks guys for the responses, quite interesting what you found Damo - what website did you find that from? I imagine that most websites simply copy from other websites - I've read almost identical scripts on various websites. It seems to appear more often than not that the serpent is devouring a person rather than giving birth. I haven't found a good reference to confirm the giving birth part. There's even a website that goes on to try and link the design back to Mayan history... When I get a good bunch of info from reliable sources together (perhaps a visit to the library too), I'll put the history up!
In the meantime, please keep posting your collective knowledge!