Mine became ill about a week before due date. Wouldn't eat with out being hand fed for the first 2 days, but continued to drink. She was a bit overweight before being bred and was carrying a very large litter, so she didn't outwardly show any signs of losing weight. Continued forcing nutrition to her for the next 2 days by trying to tempt her with an assortment of tidbits and hand feeding, as well as nutria-cal, and adding broth to her drinking water. 3 days prior to due date, she starting seizing, rushed her to the vet (at 9pm of course) and we got her back. Incredibly low blood sugar. Left her there and they continued to monitor the next day, they got her eat a little bit of canned high calorie dog food and we mixed some more into her water, as well as continued with lactated ringer I.V. We scheduled C-Section for the next evening, which was her due date anyway, in order to give her time to get her strength back. Well, she didn't want to wait that long, delivering two pups the morning of scheduled C-section but was too weak to continue on her own, so onto the table she went. Vet delivered an additional 11 pups (one DOA, had been dead for at least 3-4 days according to vet). Vet stated that her uterus was very friable and she had some tears with bleeding into her abdomen, so he needed to remove the uterus. It was just after he finished putting in the last stitch when he said "well that went extremely well," when my dog's heart stopped. He tried doing everything he could to revive her, but was unsuccessful. My vet was devastated, I was extremely moved that he cared so much for my dog. He sent in samples and called a number of colleagues and vet schools to find out what went wrong. They figured that it was a fluky liver disorder that caused her to go into ketosis.
So not only did my dog die, but I now had 12 pups to hand feed, and did I mention that it was Christmas Eve? I lost one pup, a female that started fading at day three and after three days of struggling and no weight gain, we elected to gently put her to sleep. The rest went on to become great family pets, some of which get to retrieve the occasional duck and goose.