Reproductive Control in the Bitch after Unplanned Mating (Misalliance): A Comprehensive Narrative Review

Abstract

Unplanned or unwanted mating, commonly referred to as misalliance or mismating, remains one of the most frequently encountered reproductive emergencies in small animal veterinary practice. The clinical management of misalliance in the bitch has evolved substantially over the past four decades, transitioning from the widespread use of oestrogenic compounds—which carried significant risks of bone marrow suppression and potentially fatal aplastic anaemia—to more targeted pharmacological strategies that exploit the unique endocrinology of canine pregnancy. The domestic bitch is unusual among domestic species in that the corpus luteum is the sole source of progesterone throughout gestation, with no placental progesterone production, rendering pregnancy entirely luteal-dependent. This characteristic has permitted the development of highly effective abortifacient protocols based upon progesterone receptor antagonism, luteolysis through prostaglandin administration, and suppression of the luteotrophic hormone prolactin via dopamine agonists. Aglepristone, a synthetic antiprogestin, has emerged as the most widely used and best-characterised agent for pregnancy termination in the bitch, demonstrating efficacy rates exceeding ninety-five per cent when administered during the first half of gestation. Combination protocols employing aglepristone together with prostaglandin analogues or dopamine agonists such as cabergoline have further improved success rates, particularly in mid- to late-gestation cases. Surgical ovariohysterectomy remains the definitive option when future breeding is not desired or when medical contraindications preclude pharmacological management. This review provides a comprehensive appraisal of the physiological basis, pharmacological mechanisms, clinical protocols, efficacy data, and safety profiles of the principal methods available for reproductive control following misalliance in the bitch, drawing upon evidence published in the peer-reviewed veterinary literature.