How to Recognize the Early Signs of Pregnant Dogs
If your dog has been in heat and you suspect or know that she has mated with a male dog, you need to know the early signs of pregnancy. Once you are sure that your dog is pregnant, take her to the vet so he can help you prepare for the care of your dog as well as the birth of her puppies. A dog's pregnancy only lasts 63 days on average, so the earlier that pregnancy is detected, the better.
Weigh your dog. Depending on the breed, a dog may gain 15 to 25 percent of her body weight while pregnant.
Check her nipple size. If her nipple size increases over a short period of time, your dog may be pregnant.
Gently feel your dog's belly for swelling. Do this while the dog is standing. If she is pregnant, you will feel multiple swellings. This can be done about 20 days after mating.