I mated my bitch 5 weeks ago and this is a very important and long awaited litter. Progesterone tested and took the bitch to the dog and got a very good, quick mating with a 20 mins tie. It was a four hour journey and so we decided as the mating was so good we would just have the one mating. Straight away she has acted differently, very quiet, not particularly active and has had a mucous discharge so was absolutely convinced we would have the litter. Took her to the Vets at 4 weeks and he couldn't see anything. Have to say I was shocked because I was so convinced. She has started only eating half of her morning meal and yet is barking for her second meal. I spoke to a friend and her vet told her he could see two pups and the bitch went on to have 9 as the others were tucked up. I am wondering if it is at all possible that all are hidden from view at 4 weeks. Also perhaps only a  couple of pups or do you think I am just kidding myself. If only a couple of pups when would I expect to see the body size change (if at all). Lots of questions going through my head. This is a VERY special litter for me as she is a daughter of my dog who I lost one year ago.
Thanks for any ideas

Sonography is entirely dependent on the skill of the operator.
I had a vet US a slim, muscly Boxer bitch of mine at 30 days and he found nothing.
She went on to produce SIX big strapping girls....never even offered me my money back.
Needless to say I use an expert now ..one who can almost tell me what markings they will have... :-)

Its still early days...I had a bitch scanned at 5 weeks..told possibly one pup if any..she had nine! I think scanning is only as good as the equipment used and the person scanning. I have a bitch now same as you 6 weeks pregnant....she has been confirmed in pup but two vets gave different results..one saw one puppy another saw 3....tbh she looks bigger than her mother at this stage so I"m thinking another big litter. You could wait and have her xrayed then you will defo know for sure.
I hope your girl is :)

Have only ever had 2 of my girls scanned, the first one saw 3 pups and there were 6, the second was 4 pups and she had 8. So not had it done since.

Very disappointing.
My girl was scanned on day 32, got the first mating on the day advised by Idexx. US yesterday and she is empty. She didn't really get any bigger but has become grumpy with the others. I'm fed up now but will look forward to a spring litter instead.
I think if the scanner was experienced (as mine is) then there's not a lot of hope unfortunately.

Had my bitch mated 1st sept good mating ... 2/3 wks later clear discharge .. had my vet palpate  day 29 couldnt feel anything went back wk later palpate again still nothong to go back next wk going to scan her .. she very grumpty towards other dogs has been sick last couple of wks and she following me every where ... fingers crossed

Had my girl back today at vet still cant feel anything but has developed a bit off mammary tissue vet wants to see her in 2wks . This would be her on day 42 so have just decided to have some blood drawn and check for relaxin...surely vet would have felt something by now .. aaaarrrrg

was she scanned this time a that would definitely sow something now even if it is harder to see numbers

Got scanned monday to check for infection as she is discharging white fluid now .. NO infection everything looks healthy but No pups seen either ... putting on lot of weight has become very wide at ribcage and refusing to fun this defo not like her as she would run all day after her ball .. confused lol

I would like to firstly say that I am NOT an experienced breeder, my girl only having had one litter with a sire that I own, but I would like to just tell of my own experience.  My girl didn't show at all until about 6 weeks and didn't "fully blossom" until week EIGHT!  She had four puppies.  Someone I know mated her bitch with a dog and she didn't show until week 7 and then unless you knew the bitch, you wouldn't have been able to tell at all. A very tiny Lhasa Apso, I knew she was pregnant because I recognised the "drumskin" feel to her tummy that my own girl had had and although she hardly showed, she went on to produce SEVEN puppies!!!   Where they had been hiding is anyones guess but she produced seven babies!
I think it's very hard to tell with bitches how many they are carrying a lot of the time and I would use US only to confirm she was pregnant and not to clarify how many.

MV