PetMD lists behavioral changes, nesting, attempting to nurse, enlarged mammary glands, restlessness, lactation and a swollen abdomen as signs that a female dog is affected by a phantom pregnancy. The symptoms vary somewhat between dogs, especially since several different conditions can cause phantom pregnancies.
PetWave explains that phantom pregnancy is often caused by the dog's body overreacting to normal hormonal changes, especially when there are elevated levels of the progesterone hormone. In general, a female dog affected by a phantom pregnancy starts showing symptoms roughly 6 to 12 weeks after the end of her previous heat cycle. In some cases, the symptoms are fairly minor and may include agitation, whining, appetite changes and mild depression; however, severe cases can lead to aggressive behavior, vomiting and anorexia.
Because phantom pregnancies can often convince even the most experienced breeders, PetWave explains that a skilled veterinarian needs to perform a complete physical examination on any dog who may be pregnant. Ultrasound and radiographs can determine conclusively whether or not the dog is pregnant. No further testing is required. These tests also rule out the possibility that the dog is suffering from “pyometra,” a serious condition in which pus builds up in the uterus due to a bacterial infection.