I already answered this recently... Hmm. Oh okay, the serial number at the end of the link is different, it was duplicated and one of them was deleted.
I don't have my own experience, because I don't have a dog that has had puppies. I don't live with a dog that was fuck by a male dog. These are my own wolf laws.
Based on the experiences of others, the vagina becomes wider after giving birth, but over time it narrower back to the normal size, as if no puppies were born. No other changes are mentioned, her behavior has neither improved, nor worsened. Stays the same.
In one case, I read that a zoo-virgin dog had puppies, but during the mating the male dog caused great pain and because of this later on it she was very difficult to accept human approach. Because the female dog expected him again due to bad experiences, will get pain. It took a lot of care and slow progress for her to finally accept sex with humans, and she was no longer bred with male dogs.
Both backyard and official breeders may occur this type of condition of sale that the dog must produce puppies. No matter where I bought a dog, my first condition was that it was prohibited. Further breeding, going to exhibitions and competitions, cooperative husbandry, having a say in the dog's life, etc. I forbid all of these, and I did not buy a dog from any breeder that did not accept this.