We had a litter 4 weeks ago (28th May) it was all traumatic and ended up with a cesarean - she had one uterine horn full of monster puppies and one full of tiny pups. We ended up with 2 live puppies, both boys - one twice the size of the other.
The big boy has done really well, gained weight etc and after the first week the little one started to gain weight. Now at 4 weeks the big one weighs 1kg, the little one 500gms.
The problem I have is that the little one was up on his feet last week, at 3 weeks, the big one just seems unable to get up on his back legs. He can move them really well, he wriggles about and pulls himself along very occasionaly getting those back legs under him but not pushing up. There doesnt seem to be any discomfort or pain.
I wondered if anyone else had has any experience with this - do you think he is just to fat and heavy and therefore behind, or could there be something wrong. I have more or less decided to give him another couple of days and then go to the vet - i would just like some other opinions as I havent come across this before. Apart from the walking he seems to be developing perfectly and on time.
My breed has no particular inherited health problems or hip scoring needed.

I have never had one myself but it sounds to me what is called a 'swimmer'. Its just when they are too heavy and fat to get up and about properly. Its quite common with singleton pups. There is a way of strapping them up that helps get them right but i'm not too sure what it is. Perhaps googling swimmer might find some information. Or perhaps someone will be along with some experience of this to help you more. I think if you put rolled up towels and obstacles around the whelping box so he has things he needs to climb over, this can also help.

Mel.x

Peaches has got this one correct and sound like you have got a "swimmer".  Should be OK as long as you can give the pup some help at this stage. The chest might look flattened with the extra weight the pup is carrying which has made it too heavy to enable it to get the hind legs under the body to stand up. Try keeping the pup in its side and not laying on its chest. I have been told by others they have tied the front legs together for a time to stop the pup laying on its chest for long periods. I only ever had one swimmer, a singleton pup, and did not have to resort to tying the legs. It's most likely the large quantity of milk consummed that has turned your pup into a little porker!

Ruffle up the bedding so it has ridges across it so the pup has something to grip and push its hind feet against. Also very gently flex its hind legs into the correct standing position so its stifles and hocks get manipulated into their normal position and are not out flat. With a few days of the right help the pup should be up on its feet and toddling about.

I had one like this in a litter last year (small litter too).  I was really worried and didn't look like the typical swimmer.  I used to bring him out on the carpet and hold his head up and his stomach and get him to walk.  I still feel that he was just toooo fat!  By the time I sold him he was moving around a lot better and now I believe is an extremely fit dog that goes swimming in the sea most days.

thank you for your replies - I have spoken to two of the very experienced breeders in my breed and found out how to deal with this.

But thank you for the diagnosis - something I had heard of but hadnt put two and two together.

Thanks again