Spontaneous abortion occurs at different stages of pregnancy. Depending on how far the pups have developed, they will either be reabsorbed by the mother’s body, or delivered as stillborn pups. It is possible that one or more puppies are aborted and the rest of the litter are delivered as healthy pups. You may see no signs of illness in the mother. Illness or infection of the mother may cause abortion, or abnormal development of the pup may cause early puppy death.