Identifying risk factors for canine dystocia and stillbirths.

Canine dystocia is a common problem that increases the risk of mortality to the dam and stillbirths for the pups. Understanding the risk factors for dystocia and stillbirth can help guide decision making to improve outcomes of whelping management. This study aimed to 1) evaluate risk factors for canine dystocia; and 2) assess risk factors for stillbirth in puppies, by examining all whelpings and puppies born in two breeding populations of guide dogs for a defined period of time. Dystocia risk factors were evaluated using a repeated measures model on 2,489 litters with an overall dystocia rate of 23.8%. Risk factors identified for dystocia were colony, litter size, and age of dam. Small litter size (<5 pups) had the highest dystocia rate of 36.5%, large litter size (>9 pups) had an intermediate dystocia rate of 26.9% and medium litter size had the lowest dystocia rate of 22.1%. Dystocia risk increased as the age of dam increased. Stillbirth risk factors were evaluated for 19,577 pups and the overall stillbirth rate was 5.9%. Risk factors identified for stillbirths were dystocia, litter size, cesarean section performed and breed. Pups from litters that had dystocia were 2.35 times more likely to be stillborn compared with normal litters born without dystocia. Stillbirth risk increased as litter size increased. Pups from litters of 11 or more pups were 1.45 times more likely to be stillborn. Specific information was available for a subset of pups and was used to evaluate the association with stillbirth. Low birth weight was associated with increased stillbirth risk but large pups were also at higher risk of stillbirth compared with average size pups. Stillborn pups had longer mean (102 vs 65 min) and median (47 and 32 min) inter-pup intervals compared with live pups. The positive predictive values for stillbirth were 13.5%, 28.4%, 31.8% and 36.5% when inter-pup interval threshold was set at 1, 2, 3 and 4 h respectively. There is a tradeoff between over diagnosing stillbirth and increased positive predictive value for stillbirth when inter-pup interval threshold is extended but the improvements were modest after 2 h. The last pup born in a litter regardless of litter size was significantly more likely to be stillborn. In conclusion, this paper details data driven parameters to use when making the decision to intervene during whelping that optimize survival for dams and puppies.