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Risk factors affecting parturition and neonatal mortality: a retrospective study in 1614 bitches

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Risk factors affecting parturition and neonatal mortality: a retrospective study in 1614 bitches

  1. 1. Risk factors affecting parturitionRisk factors affecting parturition and neonatal mortality:and neonatal mortality: a retrospective study on 1615 bitchesa retrospective study on 1615 bitches E. Fontaine ¹, C. Million ¹, X. Levy ¹, A. Grellet ¹ and A. Fontbonne ¹ 1: CERCA, Alfort National Veterinary College, 94700 Maisons-Alfort (Paris), France. efontaine@vet-alfort.fr In the dog, dramatic fetal losses may occur when whelping is not correctly managed. The wide range of clinical factors that owners and veterinarians have to take into account, and sometimes the complexity to diagnose dystocia, may be quite confusing. Surprising- ly, few studies had been carried out on this topic (1). The aim of this study was to point out the risk factors affecting parturition and neonatal mortality in order to help veterinar- ians to anticipate dystocia, and to let them know early enough how and when a medical supply is required. Data on 1615 pregnant bitches having been seen in consultation between January 1989 to December 2002 were collected in a database. Age ranged between 1 to 9 years (mean 3.5 years). 124 pure breed bitches, dispatched into 10 different groups according to Inter- national Cynologic Federation (FCI) classification (Fig 1), were included in this study. A statistical analysis was 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). Statistical tests were chosen according to the variables taken into account (Chi2, vari- ance analysis or linear regression). Whelping occurred in average 62 days post-ovulation (SD = 2.6) and lasted 6.9 hours (SD = 5.6). 84% of bitches had an eutocic parturition. When dystocia occured, 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, Fig 2), weight (>71 kg, p<0.01, Fig 3 ), number of pups per litter (<5.9 pups/ p<0.01, Fig 4), duration of parturition (>11.0 h/ p<0.01, Fig 5) and age, only in case of primiparous bitches (>4 years/ p=0.02, Fig 6). Fig 5: Whelping conditions in relation to the dura- tion of parturition (in 728 bitches) *duration between beginning of stage II labour up to the birth of the last pup Whelping condi- tion Number of bitches Mean* SD Eutocia 684 6.6 5.4 Dystocia 30 11 6.1 C-section 14 9.8 6.3 Whelping conditions Number of bitches Mean number of pups/litter SD Eutocia 1297 6.4 3.1 Dystocia 47 5.9 3.2 C-section 198 5.3 3 Fig 4: Whelping conditions in relation to num- ber of pups per litter (in 1542 bitches) 0 2 4 6 8 10 12 14 16 18 20 <58 59 60 61 62 63 64 65 >66 Pregnancy lenght (from ovulation to parturition) Fig 8: Neonatal mortality rate in relation to pregnancy lenght Neonatal mortality rate (%) Whelping con- ditions Number of bitches Neonatal mortality rate (%) SD Eutocia 1297 10.7 20.7 Dystocia 47 37.4 31 C-section 198 26.9 33.3 Fig 10: Neonatal mortality in relation to whelping conditions in 1542 bitches This clinical study enlightens, on 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 as early as possible bitches that may require a medical assistance during parturition. Fig 1: Breed categories according to FCI considerations Factors that appeared to be highly correlated to neonatal mortality were the breed catego- ry (group 5: primitive, spitz and nordic breeds; p= 0,02, Fig 7), abnormally short or long duration of pregnancy (<59 days or >65 days after ovulation; p<0.02%, Fig 8), number of pups per litter (<5 or >10 pups; p<0.01%, Fig 9), the occurrence of dystocia versus euto- cia (p<0.01, Fig 10) and the duration of parturition (p < 0.01). This study underlines the incidence of dystocia in molossoïd dogs. The duration of parturition could either be a cause or a consequence of dystocia. The risk of dystocia increased significantly in parallel to the duration of parturition (p < 0.001). All parturitions exceeding 11 hours were dystocic. It seems necessary to dia- gnose dystocia at an early stage, as a long duration of parturition is significantly linked to an increase in neonatal mortality. These data also confirm that the optimal lenght of pregnancy is between 59 and 65 days after ovulation. Prematurity occurs below 59 days, which is similar to the results of ano- ther study(2). Bitches with only one pup (« single pup syndrom »), are known for uterine inertia and increased neonatal mortality rates, which is confirmed here (Fig.9). Furthermore, this study enlightens that risks of dystocia and neonatal mortality are lower when the litter size is between 5 and 10 pups. References: 1: Darvelid AW, Linde-Forsberg C. 1994: Dystocia in the bitch: A retrospective study of 182 cases. J. Small Anim Pract 35: 402-407 2: Camann W.R., Ostheimer G.W. 1990: Physiological adaptations during pregnancy. Int. Anesthesiol. Clin. 28:2-10 Breed Catego- ry Number of bitches Description Examples 1 350 Sheep dogs , cattle dogs German sheperd, Australian cattle dog 2 566 Guard dogs, Molossoids breeds Pinscher, Great Dane, English Bulldog 3 201 Terriers Yorkshire Terrier, English Bull Terrier 4 13 Dachshund Dachshund 5 37 Spitz, primitive type Alaskan Malamute, Basenji 6 17 Scenthounds and related breeds Beagle, English Foxhound, Basset Hound 7 55 Pointing dogs Weimaraner, English Pointer 8 115 Retriever, flushing dogs, water dogs Golden Retriever, Cocker spaniel 9 196 Companion and Toy dogs French Bulldog, Chihuahua 10 65 Sighthound Greyhound, Whippet 0 2 4 6 8 10 12 14 16 18 20 1 2 3 4 5 6 7 8 9 10 Breed category (FCI classification) Fig 7: Neonatal mortality rate in relation to breed category Neonatal mortality rate(%)

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