Just read this article, to clarify it't not something I have or intend to do, but it does throw up some interesting points..
https://whelpingpuppies.com/breeding-a-female-dog-back-to-back/?fbclid=IwAR06So1DEqGyZOC-YJ7zqJLikecyHS7NHUj03g7aGFNYqHWFTlsMQk6LgMs

I dont breed as u know but interesting reading and learning

While not exactly a back to back mating, I've had a bitch whelp twice in less than a year.

I had a particularly good bitch and it was a breed that needs breeding early.  I have them spayed by 4 years old, and most only have one litter (or none.)

This girl was mated on her second season, as is normal for such a tiny breed.  She whelped towards the end of January, two pups, both superb.  I made the decision that she would have a second litter.  She was rested on her next season, then mated on the next.  She whelped at the beginning of January, 2 more lovely pups.

Because she didn't go 6 months between seasons, the result was 2 litters close together.  She was perfectly fine and I have never regretted it.

Things may have changed, but the UK KC wouldn't register a litter from the same bitch, within a 12 month period.   However, obviously if a bitch, like most of mine, cycles every 8 months, then you could do back to back breeding.  

I'd not want to do that, preferring to give mine a chance to have a non-productive heat at least, between pregnancies.   I did know of some breeders in America who, after having a lot of trouble getting one of their bitches in whelp, after they did manage that, mated her again on her next season.    For me, it would also matter how big the first litter was, and of course, the condition of the bitch after she'd finished nursing that first litter.  Also probably her age.  Again as we only bred for the next generation, I had no reason to need to do back to back matings.

>Things may have changed, but the UK KC wouldn't register a litter from the same bitch, within a 12 month period.

That was changed for 'ordinary' breeders years ago. I gather it's only licenced breeders that it applies to, although it might be Assured Breeders as well.

> Things may have changed, but the UK KC wouldn't register a litter from the same bitch, within a 12 month period.

My bitch didn't have a full 12 months between her 2 litters and the registration was never even questioned.  Although it was at least 15 years ago now.

> UK KC wouldn't register a litter from the same bitch, within a 12 month period

This unfortunately(in some cases) is not true, I have seen many bitches, within my own breed, in the BRS having a litter less than 12 months between(obviously I wouldn't know the ones which would have a season between).

I gather it's only licenced breeders that it applies to, although it might be Assured Breeders as well.

No does not apply to ABs either.

> This unfortunately(in some cases) is not true, I have seen many bitches, within my own breed, in the BRS having a litter less than 12 months

That being the case, it's TRAGIC.   Just my opinion.

From the KC ----

"It is strongly recommended that both Kennel Club Assured Breeders and non-Kennel Club Assured Breeders should use the following schemes, tests and/ or advice.

Bitches under two years not to produce a litter
Bitches not to produce more than one litter in a twelve month period"

True, it not now stated that litters from the same bitch within a 12 month period, won't be accepted for registration.   I wonder why that was altered.   It's now just 'strongly recommended'.

>True, it not now stated that litters from the same bitch within a 12 month period, won't be accepted for registration.   I wonder why that was altered.   It's now just 'strongly recommended'.

There are several reasons; if a large-breed bitch has a very small litter she can be back to full fitness 3 months after whelping, and mating her at the next season will do no harm.  bitch might have a short gap between seasons and have a clear season between littrs and still whelp at under 12 months from the last. And also repro vets say that it's actually healthier!

>Bitches under two years not to produce a litter

Plus, of course, bitches need only be 12 months old at the time of mating for the litter to be registered. From the KC website "Are there any restrictions that would prevent me from registering my pedigree puppies?: "The dam was under one year old at the time of mating, "

I had a bitch who whelped a litter 26th of April 2005 and 24th of April 2006. I'd have been somewhat upset if I'd not been able to register the second litter just because they were born 2 days less than a year later. I believe cases like these are the reason for why the KC changed the rules.

> I had a bitch who whelped a litter 26th of April 2005 and 24th of April 2006. I'd have been somewhat upset if I'd not been able to register the second litter just because they were born 2 days less than a year later. I believe cases like these are the reason for why the KC changed the rules.

Just out of interest, what’s stopping breeders in cases like this from simply claiming that the pups were born a few days later than they were? Apart from their own honesty, of course?

> what’s stopping breeders in cases like this from simply claiming that the pups were born a few days later than they were

Nothing, I suppose, other than the litter would have had to have been born within a normal gestation period, if the registration papers have to be signed by the owner of the stud dog.   Not so much a problem if an 'inside' stud was used

I imagine breeders also tweaking the days when the puppies are born at around Crufts time, to ensure that they can be entered in the puppy class next year Not a big deal if couple of days either side.

I'd never dream of altering a litter's date or birth.

I’ve a friend with a dog with two birthdays- his real one and his official one which was changed to fit in with a show date

There are trains of thoughts and some scientific evidence now that it’s healthier for a bitch to breed back to back and spay when she’s done. Each season spent not bred carries risks. But I suppose it depends on the bitch; it could be harmful for a bitch who has not come back into condition. I can’t say I would do it myself but I can see the logic when I read about it.