Dystocia in the Bitch Epidemiology, aetiology and treatment

Dystocia means difficult birth or inability to expel foetuses through the birth canal. The aetiology of dystocia may be maternal or foetal. Primary uterine inertia is the most common reason for dystocia in the bitch approaching 75% of the cases. The objective of this thesis was to investigate the incidence of dystocia and to find causes of primary uterine inertia. Also the treatment regimes for bitches with primary uterine inertia were evaluated. An epidemiologic investigation was performed. A large animal insurance database was used which covered healthy as well as diseased animals over time. Incidence of dystocia and the frequency of caesarean section in affected bitches were calculated. The overall incidence of dystocia was 5.7 cases per 1 000 dog years at risk. The frequency of caesarean section in bitches with dystocia was 64%. The other three studies included healthy bitches and bitches with abnormal parturition and the hormonal concentrations were analysed. An increase in prostaglandinF2α-metabolite concentration was observed from the last week of pregnancy. At labour stage II the plasma concentrations of prostaglandinF2αmetabolite, oxytocin, vasopressin and cortisol all increased in normal labour. Bitches with primary uterine inertia had plasma concentration of prostaglandinF2αmetabolite which was significantly lower compared to the normal bitches. The serum electrolytes was analysed in bitches with normal and abnormal parturition. No evidence was found indicating that abnormal serum concentration of electrolytes was a cause of primary uterine inertia in the bitch. Evaluation of two different treatment regimes revealed no significant difference in labour outcome if the bitch was treated with calcium solution in combination with oxytocin or with oxytocin only. In summary, this thesis provides information about the incidence of dystocia which was earlier unknown. The results suggest that abnormal release or production of prostaglandinF2α may be a cause of primary uterine inertia in bitches.