False pregnancy is a common condition of female dogs in which they display signs of pregnancy despite not having been mated.
Owners become concerned that they have not been as vigilant in keeping the bitch away from male dogs as they thought when they observe their pet putting on weight and developing mammary tissue even to the extent of producing milk.
Some bitches undergo quite marked psychological changes at this time which lead the owner to suspect that there is something quite seriously wrong. The bitch may go off its food, become very nervous and hide in a quiet place.
It may curl itself up, often growling when approached. Sometimes it guards a slipper or a toy and cannot be persuaded to come for a walk or play in the usual manner. These changes typically occur about two months after being in season.
Some breeds seem more prone to develop false pregnancies than others. Hounds, especially dachshunds and small terriers are most frequently affected. The condition is seen even in young dogs after the first season but it is most common in the two to six year age group.
The changes observed in false pregnancy are brought about by the presence of the hormone progesterone in the blood stream.
After estrus and the shedding of the egg from the ovary, a body called the corpus luteum develops. This produces progesterone and persists in the unmated dog for about 30 days after estrus. In the pregnant dog the corpus luteum produces progesterone over the period of pregnancy.
Progesterone stimulates the development of mammary tissue and produces the protective and mothering instincts in the female. In some bitches the corpus luteum does not regress even if the dog is unmated and it is the presence of progesterone in the bloodstream for longer than normal that is responsible for the symptoms of false pregnancy.
Treatment of false pregnancy is not always necessary. Where the level of progesterone is not very high only mild symptoms occur. The bitch may put on more weight, particularly over the back and flanks, and there may be some mammary development, but otherwise the dog is quite normal.
Where marked changes occur in the dog’s behavior, such as depression, reluctance to eat or exercise and unpredictable aggression, veterinary advice should be sought.
Treatment is relatively simple and is in the form of hormone tablets given over a period of two weeks. There is some evidence that dogs that have repeated false pregnancies may be more prone to develop mammary tumors and possibly infections of the uterus.
For this reason it is probably advisable to desex dogs that have repeated false pregnancies. Mating the dog seems to have little effect, as false pregnancies return after each season when the dog is unmated.