There are a variety of myths about pregnancy. Many people think that because dogs are closely related they will not mate. Nothing could be further from the truth. Any dog that is able to mate a bitch left unsupervised while she is in season will do so. Consequently unplanned pregnancy is relatively common.
Pregnancy is a significant medical risk for a bitch and so unplanned pregnancy should be terminated. There are now very effective drugs that can be given by your vet to ensure your bitch doesn’t have puppies from a mis-mating so you should consult your vet as soon as you think your bitch might have been mated.
Your vet may advise you that it is just as easy to have your bitch spayed during pregnancy to get rid of the puppies and to prevent accidents in the future. If the pregnancy is in its early stages this is usually safe but it is not generally advised late in pregnancy.