Whelping complications

Question
Please could you throw any light on the complications my Chihuahua bitch has had when she whelps. My own vet was not at all helpful, and simply said I should spay her... and made me feel gulity for breeding her! I have been a hobby breeder for 30 years, and never come across this before.
Background: Coco is a normal healthy 2kg, 3 year old Chihuahua bred by myself, and I have her mom, dad, granny, gt.gran. & gt.gt.gran. The unrelated father has sired several healthy litters.
Coco has an uneventful pregnancy, but upon delivery either on, or very close to her due date, she delivers underdeveloped/immature looking pups which are completely inside the placenta, like a broad fleshy band enveloping their stomach and torso areas. She has now repeated this today for the third time (only one pup present, two first and last time). In each case, the pups were either stillborn or did not survive very long, even with intensive care. I will of course retire her now, but what on earth has caused this?
Kind regards,
Shirl

Answer
Hi Shirl

I have seen this once before in a bulldogge we bred. It was the same situation for us, she was 5th generation with no problems before or after with any of that line.

Our vet was very interested as were we as to what would cause this for a healthy dog.  We did tests on the pups and it was determined that the female had contacted a low grade infection that allowed the pups to start developing. The litter was a litter of 12 and all the pups had different stages of development.

Because the female's immune system plunges when they go into season something as simple as a urine infection or scratch from the mating process could cause this.

Now before every breeding all our females go on a low dose of antibiotics for a week prior to breeding to ensure there is no undetectable issues.

Good luck