Long stinkin' pregnancy

[Sarah Conte]

Hey all-
My Viola and Othello's first litter was born 45 days ago.  I noticed them
mating the day after the pups were born, and yet she has not delivered.  The
first litter was huge -seven pups- who are all still alive and she is now
looking pretty big again.  Has anyone heard of a pregnancy going this long
before?  She was starting to look pregnant again when the pups were about 3
weeks old, but didn't start getting really big until a few days ago.  
Suggestions? Clues? Comments?
Thanks :)
Sarah