In the dog, dramatic fetal losses may occur when whelping is not correctly managed. The wide range of clinical factors that have to be taken into account, and the complexity to sometimes diagnose dystocia, may be quite confusing. The aim of this study was to point out the risk factors affecting parturition and neonatal mortality in order to help veterinarians to anticipate dystocia, and to let them know early enough how and when a medical supply is required
Material and Methods
Data on 1615 pregnant bitches were collected in a database. Age ranged between 1 to 9 years (mean 3.5 years). The bitches belonged to 124 different pure breeds, dispatched into 10 different groups according to International Cynologic Federation (FCI) classification. Statistical analysis were carried out to study the correlations between maternal and fetal dystocia, neonatal mortality and the following parameters: age, breed category, weight, number of previous whelpings, duration of parturition, number of pups per litter and pregnancy length (from the day of ovulation estimated by plasma progesterone assays).
Whelping occurred 62 days post-ovulation in average (SD = 2.6) and lasted 6.9h (SD = 5.6). 84% of bitches had an eutocic parturition. When dystocia occurred, a C-section was performed in 81% of the cases. Altogether neonatal mortality rate was 13.7% (SD = 24.3), and 37.5% of the litters were concerned. Factors that appeared to be highly correlated with dystocia were the breed category (group 2: guard dogs and molossoids / p<0.01), weight (>71 kg, p<0.01), duration of parturition (>11.0 h / p<0.01), number of pups per litter (<5.9 pups / p<0.01) and age, in case they were primiparous bitches (>4 years / p = 0.02). Factors that appeared to be highly correlated to neonatal mortality were the breed category (group 5: primitive, spitz and Nordic breeds), the occurrence of dystocia versus eutocia (p<0.01), pregnancy length, in case of parturition occurring before 59 days or over 65 days after ovulation (p<0.02%), number of pups per litter, less than 5 or over 10 pups per bitch (p<0.01%).
Discussion and Conclusion
This clinical study enlightens at a large scale specific factors increasing the risk of dystocia or neonatal mortality in purebred bitches. As such, it may be helpful for veterinarians in order to detect in advance bitches that may require a medical assistance for parturition. Concerning neonatal mortality, the optimal time of parturition was found to be between day 59 and 65 after ovulation.