Preparing for whelping
As the due date nears, set up a quiet whelping box in a warm, draft-free spot and let your dog get used to it ahead of time. Have clean towels, a heat source for the puppies and your vet's number ready. Begin taking your dog's temperature twice a day in the final week; a clear drop often signals labor within 24 hours.
Why dating from the LH surge is more accurate
Counting from the mating date is convenient but approximate, because conception can lag mating by several days. Breeders who use progesterone testing can pinpoint ovulation and the LH surge, after which whelping is very consistent at about 65 days. If you have that testing, use those dates for a tighter estimate.