Pseudopregnancy in Small Animals

Physiologically, all nonpregnant bitches are "pseudopregnant" at the end of diestrus but the intensity of these signs can be extremely variable among bitches. Some bitches have no signs, whereas others show conspicuous signs and this is called overt pseudopregnancy.

It is thought that the abrupt drop in progesterone at the end of diestrus plus the hormone prolactin plays a central role in the pathogenesis of pseudopregnancy, which is why it can be brought on by ovariohysterectomy or ovariectomy during the luteal phase.  However, its exact pathophysiology is not completely understood.

Behavioral signs of overt pseudopregnancy include:

• ­restlessness

• anorexia­

• decreased activity­

• licking at abdomen ­

• aggression ­

• maternal behavior

Physical signs include ­weight gain, ­mammary enlargement, and­ milk secretion.

Diagnosis of overt pseudopregnancy is based on compatible clinical signs in a nonpregnant sexually intact bitch. There are currently no specific diagnostic tests for pseudopregnancy because hormonal assays are nondiagnostic for this condition.

Pseudopregnancy is a treatable condition with a good prognosis for resolution, as long as the underlying hormonal cause has been corrected. Most clinical signs resolve without treatment.

Ovariohysterectomy is indicated for bitches not intended for breeding; surgery during anestrus is recommended. Surgery during the luteal phase can result in pseudopregnancy.

Prolactin-inhibiting drugs can be used to inhibit lactation. The only prolactin-inhibiting drug approved for use in dogs is cabergoline (5 mcg/kg, PO, every 24 hours for 5 to 10 days).

If lactation is occurring, do not milk out the mammary glands as this will only stimulate lactogenesis.

If a sedative is needed, phenothiazines are not recommended as they stimulate prolactin secretion.