If your dog is not spayed, it is a good idea to know the signs of pregnancy should she mate. However, dogs will sometimes show signs of pregnancy even if they are not going to become mothers. This is called pseudopregnancy, false pregnancy or phantom pregnancy, and can affect the dog physically and behaviorally.
False pregnancy in dogs usually occurs about four to nine weeks after their last heat cycle. You may notice physical symptoms such as mammary gland enlargement, lethargy, vomiting and fluid retention - all symptoms seen in pregnant dogs. The dog may also be acting like she is pregnant - nesting, mothering activities, being restless and showing a decreased interest in physical activity. Some dogs even have a false labor, then act protective of their toys or other small objects.
It is important to keep in mind that not all dogs in heat will experience this, and some dogs will have different clinical signs from one cycle to the next, according to VCA Animal Hospitals. This phenomenon happens because of the hormones produced by the ovaries after an estrus cycle. These hormones prepare a dog's body to carry puppies, whether or not she was fertilized by a male. If she is not pregnant, these signs should subside as the hormones do, after about four to six weeks, and do not require treatment.
However, if you are concerned about your dog's physical condition or behavior, talk to your veterinarian about treatment options. The vet may recommend spaying the dog, since this procedure will eliminate almost all issues related to the dog's heat cycle. VCA recommends spaying to prevent pregnancy because breeding dogs contributes to the pet overpopulation issue in the United States.
According to the American Society for the Prevention of Cruelty to Animals, spaying can also prevent a number of health issues for your dog. It can reduce the dog's risk of breast cancer later in life and will eliminate her risk of ovarian and uterine cancers.
VCA reports that it is best to spay your dog after all clinical signs of a false pregnancy have subsided, otherwise she may continue to exhibit these physical and behavioral signs for several weeks after the procedure.