The Royal College of Veterinary Surgeons, British Veterinary Association, British Small Animal Veterinary Association and the Kennel Club consider that in the interests of animal welfare, reports should be made to the Kennel Club in appropriate cases, to help correct some of the problems identified in the breeding of dogs.
See more at: https://www.thekennelclub.org.uk/dog-breeding/first-time-breeders/whelping-your-first-litter/reporting-c-sections-and-surgeries/
This page includes a link for online reporting.
"Veterinary report of a caesarean operation on a dog and/or a procedure altering the natural conformation of a dog
The owner of all dogs registered with the Kennel Club give their consent to the reporting of the following: [(1) any caesarean operation, and/or] (2) any operative procedure carried out by a veterinary surgeon on a dog which alters its natural conformation.
Veterinary surgeons carrying out such procedures are therefore asked to complete the following form (to the best of their knowledge) and submit online."
Also see the Kennel Club's resources: