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Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

English BulldogEnglish Bulldog

Dystocia due to Foetal-Pelvic Disproportion

Related terms: foetal-maternal disproportion, dorso-ventrally flattened pelvic canal

Outline: English bulldogs have difficulties giving birth. This is because there is commonly a serious mismatch between the size of English bulldogs pups and the birth canal of their mothers, caused by changes in body shape (of both puppy and mother) due to selection for particular features. This means that unassisted birth is not possible and, unless a caesarean section is carried out, the birth is likely to end in the painful death of the mother. 

Summary of Information

(for more information click on the links below)

1. Brief description

Dystocia is a veterinary term used to describe any difficulties in giving birth. Dystocia can lead to suffering during attempts at giving birth and frequently requires veterinary intervention. Birth problems are common in English bulldogs due to the puppies having relatively large heads due to brachycephaly (abnormal head shape) and the bitches having relatively narrow pelvises (Johnston et al 2001). Evans & Adams (2010) found that 86% of English bulldog pregnancies end in delivery through caesarean section. Many of these caesareans are due to dystocia but some are probably performed electively to prevent dystocia or to avoid breathing problems that the bitch may experience during parturition (another common problem in English bulldogs – see Brachycephalic Airways Obstruction Syndrome).

2. Intensity of welfare impact   

Dystocia causes severe pain and distress. This condition is complicated further in English bulldogs, because they often have pre-existing breathing problems associated with brachycephalic head shape that can lead to difficulty in coping with stress and physical exertion. Without intervention dystocia will lead to the death of the puppies and often of the mother.

3. Duration of welfare impact

Dystocia can lead to attempts to give birth (parturition) lasting for hours and possibly days if veterinary intervention is not sought.

4. Number of animals affected

The majority of pregnant female English bulldogs would suffer dystocia if allowed to give birth naturally and elective caesareans were not carried out. Currently 86% of English bulldogs births are by caesarean in the UK (Evans and Adams 2010)

From data on estimates of total dog population in the UK and on the percentage of all micro-chip registered dogs that are English bulldogs (Lucy Asher, 2011, personal communication), we estimate that the UK population size of this breed may be around 50,000.

5. Diagnosis

A diagnosis of dystocia is made if a mother fails to produce live young within defined time periods after the onset of parturition. Radiographs can be used to confirm foetal-pelvic disproportion.

6. Genetics

No specific genes have currently been identified but the problem of foetal oversize is connected with brachycephalic breed characteristics such as having a relatively short nose, and large head. It has also been suggested that English bulldogs have relatively narrow pelvises compared to other breeds, again related to their breed characteristics (Johnston et al 2001).

7. How do you know if an animal is a carrier or likely to become affected?

English bulldogs are commonly unable to give birth normally. Thus finding a puppy that has been delivered naturally is difficult.

Radiographs of the pelvis of a mature bitch may give some indication of shape abnormalities (as have been shown to be involved in dystocia in another brachycephalic breed – the Boston terrier (Eneroth et al 1999, Linde-Forsberg ND)).

8. Methods and prospects for elimination of the problem

It seems likely that breeding only from animals that have themselves been born naturally would be likely to solve the problem in due course. However, this would restrict the size of the available gene pool for breeding and it would be important to assess the risks of other genetic diseases. Another approach would be to out-breed with dogs that are not predisposed to dystocia.

For further details about this condition, please click on the following:
(these link to items down this page)

1. Clinical and pathological effects

Dystocia (difficulty in giving birth) can occur for a variety of reasons. These are generally categorised into factors that relate to the mother and factors that relate to the foetus (Jones & Joshua 1988). Both affect the English bulldog (Johnston et al 2001) and lead to a very high rate of dystocia in this breed. A recent report indicated that 86% of English bulldog litters, in the UK, are delivered by caesarean section rather than naturally via the birth canal (Evans & Adams 2010).

The maternal factor that contributes most to dystocia is a narrow pelvis (Freak 1948, 1975, Bennett 1980, Jones & Joshua 1988, Johnston et al 2001). The front of the pelvis, which the puppy must enter during the birth process, should be pear-shaped in cross section, with the vertical axis being longer than the horizontal axis (Jones & Joshua 1988). Abnormalities of pelvic shape have been investigated in relation to dystocia in the Boston terrier and Scottish terrier (Eneroth et al 1999) but, as far as we are aware, there have been no corresponding studies in the English bulldog.

The foetal factor that is most likely to cause dystocia is a large head (Johnston et al 2001). The larger the puppy the greater the risk.

The English bulldog is a brachycephalic breed. These dogs have relatively short muzzles and a high prevalence of breathing difficulties (Evans & Christensen 1979,Brown & Gregory 2005, Bannasch et al 2010). Dogs with brachycephalic airway disease have a shortened and distorted upper airway, narrow nostrils, an elongated soft palate, and an abnormal larynx (voice box). Secondary to these airway obstructions, these dogs can develop collapsed airways, especially involving the larynx and trachea. These defects commonly make it difficult for the breed to breathe adequately whilst undertaking normal activity. Stress caused by exercise, excitement, heat or giving birth can exacerbate this and lead to collapse and death.  

It is likely that a proportion of the large number of caesarean sections carried out on English bulldogs are elective procedures arranged by breeders to avoid any chance of dystocia and the risk of asphyxiation of whelping bitches as might otherwise occur during the normal birth process (Harvey 1989).

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2. Intensity of welfare impact

Dystocia is a severe welfare problem for the affected bitch and, if untreated, it will usually lead to her death. Even with treatment, dystocia is likely to result in a higher rate of death in puppies, unless treatment is prompt (Jones & Joshua 1988). Treatment of a bitch that is having difficulty giving birth involves transportation of the dog to a veterinary practice for examination and imposes further stressors for a brachycephalic dog with breathing difficulties. Uterine contractions are painful and control of this pain is difficult in the home environment, so any delay in the birth process causes more prolonged and severe pain than usual. Caesarean section is usually required to treat English bulldogs with dystocia. Unplanned, emergency caesarean sections are likely to have a higher welfare impact than either natural birth or elective caesarean, and a higher death rate for the puppies. Caesarean sections are major surgical procedures and anaesthesia presents particular risks to brachycephalic dogs because of their abnormal respiratory tracts and breathing difficulties.

It is likely that a significant proportion of caesarean sections in English bulldogs are performed electively. It can be argued that this reduces the risk of adverse welfare problems that are otherwise likely to occur because of foetal-pelvic disproportion in these dogs (Evans & Adams 2010).

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3. Duration of welfare impact

If untreated, dystocia may continue for up to 24-36 hours although, as this time goes on, mortality among the puppies will increase. After 36 hours the survival of the bitch is certainly compromised (Jones & Joshua 1988). If a caesarean is performed, there will be pain from the surgery for some days although effective analgesia should be available. A further issue is that if live puppies have been delivered and the bitch is to rear them normally then their sucking on a teat close to the surgical wound may cause her pain in the first week, or so, after the procedure.

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4. Number of animals affected

It has been reported that 86% of English bulldog litters are delivered by caesarean section rather than naturally (Evans & Adams 2010). English bulldogs are one of three breeds excluded from insurance claims for dystocia in certain parts of the world (Bergström et al 2006) because dystocia is so common that it is uneconomic for insurance companies to include this cover. The other excluded breeds are the French bulldog and the Boston terrier, which are reported to have caesarean rates of 81 and 92% respectively (Evans & Adams 2010). English bulldogs were found in a study undertaken in Canada and the USA, to be in the top five of the breeds most likely to have elective and emergency caesarians (Moon et al 1998).

From data on estimates of total dog population in the UK and on the percentage of all micro-chip registered dogs that are English bulldogs (Lucy Asher, 2011, personal communication), we estimate that the UK population size of this breed may be around 50,000.

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5. Diagnosis

A normal labour has three stages. In the first stage, the body prepares itself for birth with the cervix relaxing and dilating. During this stage, if left alone, the bitch in the wild would seek seclusion and dig a den. The second stage involves the loss of uterine fluids, progressively more vigorous straining, and birth of the puppies. The third stage of labour is delivery of the foetal membranes and, in dogs, this stage can be concurrent with the second stage, as membranes are sometimes expelled with their puppy. In some cases of dystocia, stage two never starts and dystocia is diagnosed once a dog is recognised not to have progressed from stage one to stage two after about 24 hours. Otherwise, dystocia may be diagnosed when the bitch has been in the second stage for about two hours without delivering a puppy (Jones & Joshua 1988). Radiographs can be used to investigate if foetal-pelvic disproportion is the cause and to help in judging if normal birth will be possible.

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6. Genetics

The genetic basis of foetal-pelvic disproportion in English bulldogs is that which underlies the breed’s conformational abnormalities of brachycephaly and having a narrow pelvis, both of which are associated with the breed standard. The part of the canine genome responsible for brachycephaly has been identified and two genes have been implicated (Bannasch et al 2010). There are no genetic tests to help determine which dogs are least at risk of dystocia and therefore most suitable for use in breeding.

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7. How do you know if an animal is a carrier or likely to become affected?

All female English bulldogs are at risk of this condition. All puppies have the brachycephalic head shape and many bitches are unable to give birth naturally because of this and perhaps also because of pelvic abnormalities. Thus it is very difficult to find a puppy which has not been born via caesarean section. Ideally only puppies born by natural birth from a bitch that did not have dystocia, should be used for breeding.

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8. Methods and prospects for elimination of the problem

It might be argued that breeding from dogs that had been born naturally would help to select for a strain (population) able to give birth naturally in the future. However, any advantages that might bring would have to be 'weighed' carefully against the risks associated with allowing all births to progress naturally rather than undertaking elective caesarians to preclude the risk of dystocia. .

It might be possible to assess the size and shape of the pelvises of prospective mothers, as has been described for Boston and Scottish terriers by Eneroth et al (1999). These authors found that bitches in which the pelvis was larger vertically than horizontally were less likely to suffer from dystocia. Breeding from such dogs, and from those with the greatest pelvic measurements, might be a reasonable approach and may be helpful in reducing the incidence of dystocia. However, this speculative proposal has not been validated and might be hard to undertake in practice. As yet no such scheme is in operation.

Given the high proportion of animals that appear to suffer from foetal-pelvic disproportion in this breed, efforts to breed only from a minority judged to have the best chances of giving birth naturally might risk, through diminution of the size of the breeding population, inadvertent selection for other genetic diseases.

Selecting for smaller head size in puppies is theoretically possible and, if successful, would probably help in reducing the incidence of dystocia. However, this might result also in unpredictable changes to other aspects of conformation or biology. 

Efforts directed at reducing the prevalence and severity of brachycephalic airway disease in the breed (eg by out-crossing with dogs that are not affected with this disease) would probably have an impact (through reducing the severity of the brachycephaly itself).

intervention will always be available to manage dystocia wherever and whenever these dogs may breed, and because of the stressors that can occur even with veterinary intervention, animal welfare is best served by not breeding from animals that are unlikely to be able to give birth naturally.

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9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.

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10. References

Bennett D (1980) Normal and abnormal parturition. In Morrow DA Ed Current Therapy in Therionology; Diagnosis, Treatment and Prevention of Reproductive Diseases in Animals. Pp 595-606 WB Saunders: Philadelphia

Bergström A, Nødtvedt A, Lagerstedt A and Egenvall A (2006) Incidence and breed predilection for dystocia and risk factors for cesarean section in a Swedish population of insured dogs. Veterinary Surgery 35(8): 786-91

Bannasch D, Young A, Myers J, Truvé K, Dickinson P et al (2010) Localization of Canine Brachycephaly Using an Across Breed Mapping Approach. PLoS ONE 5(3): e9632. doi:10.1371/journal.pone.0009632

Brown D and Gregory S (2005) Brachycephalic Airway Disease. In Brockman D & Holt D Eds BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery. pp84 BSAVA: Cheltenham

Eneroth A, Linde-Forsberg C, Uhlhorn M and Hall M (1999) Radiographic pelvimetry for assessment of dystocia in bitches: a clinical study in two terrier breeds. Journal of Small Animal Practice 40: 257-264

Evans K and Adams V (2010) Proportion of litters of purebred dogs born by caesarean section. Journal of Small Animal Practice 51: 113–118

Evans HE and Christensen GC (1979) Miller’s Anatomy of the dog. WB Saunders: Philadelphia, USA. pp 118–121

Freak MJ (1948) The whelping bitch. Veterinary Record 60: 295-301

Freak MJ (1975) Practitioners'-breeders' approach to canine parturition. Veterinary Record 96: 303- 308

Harvey CE (1989) Inherited and congenital airway conditions. Journal of Small Animal Practice 30: 184-187

Johnston SD, Root Kustritz MV and Schultz Olson P (2001) Canine and feline theriogenology Saunders: Philadelphia

Jones D and Joshua J (1988) Some problems of parturition. In: Reproductive Clinical Problems in the Dog, 2nd Ed. pp 87-112. Wright: London

Moon PF, Erb HN, Ludders JW, Gleed RD and Pascoe PJ (1998) Perioperative management and mortality rates of dogs undergoing cesarean section in the United States and Canada. Journal of the American Veterinary Medical Association 213: 365–369

© UFAW 2011

Credit for main photo above:

By Asmadeus (Own work) [Public domain], via Wikimedia Commons