A false pregnancy is called a pseudocyesis. A pseudocyesis occurs when an intact and nonpregnant female dog goes through a phase of mammary development and lactation and behaviors similar to that of pregnant bitches. The affected bitch often allows nursing and displays mothering tendencies. All bitches produce the hormone progesterone for two months after ovulation, which results in mammary development. When progesterone decreases abruptly near the end of the heat cycle, it stimulates the release of another hormone called prolactin that causes mothering behavior and lactation. Pseudocyesis can also occur following an ovariohysterectomy, also known as a spay surgery.

During a false pregnancy, mammary gland distention and the presence of a light-colored fluid or milk at the nipples are commonly seen. Common behavioral changes include mothering of objects such as toys in the environment, nesting, and periods of aggression. Inflammation of the mammary glands can also occur causing pain and discomfort.

Diagnosis is often based on the presence of the clinical signs and knowledge that the dog was in heat approximately two months previously. If there is any chance the bitch was bred when it was last in heat, an abdominal ultrasound may be recommended to rule out a pregnancy.

Most signs of pseudocyesis usually disappears spontaneously within two to three weeks. If milk production by the mammary glands is excessive, testosterone can be given to decrease this milk production. Spaying the dog does little for the current episode of pseudocyesis but prevents a recurrence in the future.

Continued monitoring and recheck examinations may be recommended over a two-to-four-week time span. The age at which pseudocyesis occurs is variable, and it does not occur with every heat cycle. The development of this condition may be an indicator of normal function of the ovaries and does not usually indicate a uterine disease. There is some evidence that repeated episodes of false pregnancies may lead to an increased incidence of malignant mammary tumors in the dog's later years.

Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.

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