Interested in breeder input or experience with something we have not seen in 25 years of breeding. Our girl whelped 12 puppies two days ago, 11 surviving. Just this morning I noticed the largest male has a ‘flat’ chest rather than a round rib cage. Google comes up with swimmer puppy which I understand to be more of an issue in stockier breeds and becomes apparent later, when pups start to walk. I have a medium-sized, athletic, sporting type breed (happy to specify if allowed). Not sure if this is something than could correct itself? Puppy seems absolutely normal, gaining weight, sleeps in all positions (not only on stomach). Thank you!

Are his legs sticking out to the side, or front and back like the rest of the pups? If they're sticking out to the side this is swimmers, it can be improved, some say cured but I haven't seen that, I have seen a swimmer puppy turn into an adult able to walk and run though it wouldn't win any shows. If his legs appear in the normal position it could just be a slight difference in conformation? I know a litter of silkens where most had the classic narrow, deep chest and one pup a round, barrel chest, though a lovely dog otherwise, it's just a fault like any other.

Legs are normally positioned. He sleeps on his side very comfortably which I believe is not the case with swimmers? I am hoping it is a temporary issue, like his ribcage was compressed due to crowding in the uterus, and maybe he will grow out of it. Thank you for your reply. Look forward to other feedback if anyone has seen something like this.

I had a flat puppy in a litter of Cavaliers many years ago. He was completely normal by the time he left for his new home. Do make sure that the floor of the whelping box provides good traction for his little feet. Gently massaging his legs can help too, and providing lots of soft obstacles that he can scramble over to reach his Mum and litter mates. Another friend covered the commercially sized egg trays with towelling to exercise her swimmer puppy, that worked well too.

Interesting! Thank you for your reply.

Update: Spoke with a longtime breeder/mentor and she has seen this several times, even in multiple puppies in a litter. She believes it is due to compression in utero or during the whelping process. In all instances the abnormality self-corrected in a matter of days or weeks, so I am feeling much more optimistic!

I'm not sure about that, though I believe it is usually the heaviest puppy in the litter that is affected. It was a E. Springer breeder who advised me - he had seen it several times before. I wouldn't like to repeat the mating, or breed on from a dog that I knew to have been a swimmer puppy though.
Another friend had one, (again a Cavalier), I never saw it but her vet diagnosed an inverted sternum, judged it to be non viable and euthanised it. My puppy and the one exercised on egg trays were not directly related but did share similar bloodlines, the third one had no shared breeding in the first four generations.
Good luck with your puppy.

Update: well, several days after my original post, it turns out my breeder friend was right and the puppy‘s chest is now completely normal! Glad I didn’t run to the vet for x-rays and likely dire prognosis. No matter how long you breed, you learn something new with every litter so sharing the happy outcome in case anyone else encounters this.

maye222 Swimmer Puppy: So pleased for you that there has been a positive outcome!!!   In my experience, it's always best to leave a little time for these
new borns to have the chance to recover from the birth as much as Mum before jumping in.  Many on here believe the Vet is the only way to 'waylay' fears but
there are a lot of instances when medical intervention is both unnecessary and costly.  Agree with a previous poster that flooring can be an issue but gutted the poster
who mentioned a 'displaced sternum' diagnosis meant that little puppy had to be euthanised.  So sad!