Liz Buchanan BVSc MRCVS
Hello! My understanding is that the inheritence of herniae is not so straight forward as 'if the parent has it, the babies will have it' but it does tend to run within families and lines. It wouldn't surprise me if there was one lurking further back. Inheritence is complicated and sometimes, traits can be hidden for a while (I look a bit like my Dad's Mum's Mum, for example, but the women in between us don't). Everyone carries genes in them that are not shown on the outside; if two parents carrying those 'hidden' genes are mated, then the trait might come to the fore. Not that there is a known hidden gene causing an inguinal hernia; rather a combination of genes, perhaps coding for things like the angle of the hips and the muscle coverage in the inguinal region and the position of the inguinal canal (I don't know exactly), which might come together in one pup, causing the hernia. In the UK vets frequently refuse to fix herniae while leaving an animal unneutered for ethical reasons, but this wasn't always true in the past. There may be unscrupulous breeders out there, but it's certainly not a given in a particular case.
Finally, I think that it's fairly unlikely that you will have done anything wrong to cause an inguinal hernia in a pup, although I have head people say that traumatic incidents involving abdominal compression could play a role in acquired (non heritable) cases.
Hopefully something there is useful.