I had a bitch where all four legs swelled, her calcium levels were very low, as was her RBC. My vet called Dr Hutchinson for a consult, which you might also want to do, anyway he recommended monitoring her bloodwork, and doing a c-section, strongly recommended not letting her whelp on her own.
Everything turned out fine, her legs went back to normal the puppies were all normal and healthy and her bloodwork is back to normal. It wasn't that big of a litter, there were 9, but it was her largest litter.
The swelling happened gradually, but in the last week before she was due.
