My dog has been scanned twice the first time they said she had a singleton and second time said no pups and likely to have reabsorbed but she is still very fat and showing signs of pregnancy could it be a phantom or could the scanner be wrong and pup is just hiding,a few other breeders have also said she looks very pregnant. Should I try having her rescanned or should I just wait and see if she goes into labour?

What days were she scanned at? Was it by a vet or somebody who just does scanning? What day is she on now? What pregnancy signs are you seeing? Are her teats much bigger (as in 3 times the normal size) and does she have a clear discharge? Has she been fed more than usual? Need more info. I'd always be extra cautious with a single pup as the likelihood of a c-section being needed is much bigger -especially in larger breeds, in my personal experience.

She was scanned at day 25 by something who does scanning when the one was seen and day 38 when none were seen by the same lady she is now day 40 and she is being fed the same amount as she usually would due to being told no pups and has put on a substantial amount of weight her teets are also a lot bigger and she has had a bit of clear discharge she is also a lot more tired. She’s not a big breed as she is a pug.

I've got a bitch who has regular phantoms but she's never had the discharge or gained weight. Having said that, I would not really expect to see any obvious weight gain after just 40 days -but neither of my two breeds are of a similar build to yours. If I was you I would go for another scan to play safe. And take her temperature to make sure it isn't too high as sometimes bitches can develop pyometra without many symptoms other than a high temperature.

I'd wait until she's around 2 days beyond the due date from the first mating (bearing in mind conception may not have taken place that day) and if nothing has happened, get her to your vet and be prepared for her to need a C.Section.   For sure, small litters or singleton puppies do tend to 'sit' growing bigger by the day and making it less likely there will be a natural birth.   Your vet would x-ray to see if she's empty or not, before doing a 'Section.

From my experience, false pregnancies, or phantoms tend to show after the whelping date.   But that's just my experience.