I'm getting slightly concerned that my bitches is about to go over. She is a giant breed and scanned to suggest 9 puppies. She will be 63 days from ovulation at 2am (in 16 hours) and shows absolutely no sign of starting any time soon. Having never had a bitch go by 63 days I'm getting a little concerned.

You have probably got another day, but if you took her for a progesterone test today.

http://www.peteducation.com/article.cfm?c=2+2109&aid=3201

"About 48 hours before whelping, the progesterone level drops to the 2 ng/ml range and within about 24 hours of whelping, the level drops to the 1 ng/ml range. This can help determine the proper timing of a c-section,"

Thank you B
Unfortunately, although my bitch went into spontaneous labour, her litter was born by c section as she just didn't progress quickly enough and the puppies were becoming distressed. It all seems ok so far, and despite an anaesthetic (in a breed who are known to have issues with anaesthetic) she is coping amazingly.

That is good, so did the labour start the next day?

She started on day 63 about 9am, but kept stopping and starting until 33 hours later when she stopped completely and puppies were getting distressed

Good outcome, but surprised that they didn't use Oxytocin after first puppy?  Or did she have primary Inertia?

Primary inertia. No puppies delivered at all. The vet prepared her for surgery and put a drip up then gave her an oxytocin in theatre before putting her under to see if any would come out naturally. Alas, no contractions were visible so he opened her up and got them out. I was a bit concerned about oxytocin without a puppy having passed, this is why she was completely prepped before he did, so he could open her up quickly. Luckily it all worked out in the end, even if it wasn't the way we had hoped for.