Equis ISSN 2398-2977

Reproduction: dystocia

Synonym(s): Problems foaling

Contributor(s): Terry Blanchard, David Dugdale, Herman Jonker, Rob Lofstedt, Graham Munroe, Vetstream Ltd, Elaine Watson, Madeleine L H Campbell

Introduction

  • Difficulty in giving birth, or inability to give birth unaided.
  • Incidence: approximately 4% in Thoroughbreds.
  • Cause: fetal malposture most common.
  • Signs: mare in extreme discomfort/failure of progression of foaling.
  • Treatment: veterinary intervention is required for delivery.

It is important to be familiar with normal labor in order to recognize dystocia early enough to reduce the risks to both mare and foal. Second stage of parturition may be as brief as 15-30 min.

Causes of dystocia

  • Most cases of dystocia are due to postural abnormalities of the fetus (malposture) the most common of which is a simple retained forelimb or head and neck deviation. The live fetus plays an active role in positioning ready for delivery and if weak/dead this is compromised.
  • The pelvic inlet of the mare is wide compared with other animals which can → abnormally presented foal entering the pelvis.
  • Malpresentation, eg posterior presentation with bilateral hip flexion (breech) and malposition, eg ventral oblique, are much less common.
  • Maternal causes of dystocia are not as common and include uterine inertia and torsion, hydroallantois Uterus: hydroallantois / hydroamnios, ruptured prepubic tendon Prepubic tendon: rupture, abnormal pelvis, eg due to a pelvic fracture whilst pregnant, and premature separation of the allantochorion (red bag delivery) .
  • The long fetal neck and limbs predispose mares to dystocia.

Signs of dystocia

  • The following are all signs of dystocia (depending on the cause of the dystocia – they do not all occur together).
  • At the beginning of the second stage labor Fetus: pregnancy - diagram:
    • Chorioallantois appears at the vulval lips indicating premature separation of placenta Umbilical cord: premature separation  (not always associated with dystocia, frequently seen after induction of parturition).
    • Amnion does not appear within 5 min Foaling 01: amnion at vulva - normal .
    • Fetal forefeet and/or head do not move into the pelvic inlet.
Fetal forefeet normally do not appear in the vulva at the same time, one lef is normally +/- 20 cm behind the other.
  • During second stage labor:
    • Mare stops straining for prolonged periods, ie failure for delivery to progress normally.
    • Mare shows signs of extreme discomfort, such as frequent changes of position and rolling.
    • Failure to progress despite straining.
    • Failure to deliver the fetal hips once the thorax has passed through the pelvic canal (rare in the mare unlike the cow) - usually due to impaction of hindfoot in pelvic canal due to 'dog-sitting' posture.

Assessment of dystocia

  • Check the mare's mucous membranes (color, refill time) → hemorrhage, shock.
  • Check for presence/nature of vulval discharge/fetal membranes.
  • Identify fetal extremities if visible or palpable.
  • Internal examination:
    • Perform on standing mare.
    • Use restraint, eg twitch or lip chain.
    • Generous amounts of lubricant should be used when performing an internal examination.

Beware of unpredictable behavior of the mare during the second stage of labor, and have due regard for the safety of attending personnel.

  • If stocks are used, they should be open-ended with removable sides for safety.
  • The genital tract should be checked for lesions, lacerations, contusions.
  • Pelvic abnormalities should be noted.
  • Presentation, position, posture and viability of the fetus should be assessed.

Care should be taken when performing an internal examination → active fetal response to manipulations → complicate initial simple dystocia.

Correction of dystocia

  • If mare and foal are both still viable at the time of initial examination, it is useful to have an indication from the owner of whether the mare or the foal is the priority.
  • Time is of the essence in dealing with equine dystocias. Therefore (depending on circumstances) many veterinarians/stud farms have a protocol for dealing with dystocias involving live foals which aims to minimize delay, eg attempt mutation on farm; if this is not rapidly successful transport mare to clinic. Continue attempts at mutation whilst mare is prepared for general anesthesia. If mutation not successful, anethetize mare and attempt mutation with hindquarters of mare hoisted. If this is not successful within an agreed time limit, proceed to caesarean operation.
  • The rapid, powerful and almost violent expulsive efforts of second stage parturition plus the variability of the mare's temperament make treatment of dystocia by manipulation difficult and dangerous.
  • The reproductive tract of mares is vulnerable to trauma, including obstetric procedures Vagina: trauma Perineum: trauma Uterus: torsion, and care is required to keep this to a minimum.
  • Careful, quick and safe examination of the parturient mare is essential for diagnosis of the abnormality and to develop a plan of action.
  • Examination around a door frame or behind straw bales is useful and restraint using a twitch may help in more awkward mares. The use of sedatives may depress the fetus. If required to increase the safety of the mare and of personnel during examination an alpha-2 agonist/butorphanol combination is preferred. Pulling the mare's tongue out of the mouth may decrease straining. Installing a nasogastric tube in the trachea may also help to prevent abdominal straining. If the mare is tractable, examination while the mare is walked is often helpful - particularly helpful for alleviating postural abnormalities.
  • Epidural anesthesia Anesthesia: epidural is an option but takes time for full effect and is not easy to carry out in an anxious mare. Muscle relaxants such as clenbuterol Clenbuterol hydrochloride may be an alternative; they are effective but it also takes some time for their full action. Clenbuterol competes with the physiological effect of oxytocin during parturition.
  • Short-term general anesthesia is very useful in dealing with abnormalities particularly of postural nature. An alpha2 agonist/ketamine combination +/- guaifenesin gives good relaxation and anesthesia without excessive fetal respiratory depression. Placing the mare on an incline (head down) or lifting (hoisting) the hindquarters of the anesthetized mare facilitates repositioning of the fetus.
  • In more severe circumstances general anesthesia using inhalation techniques Reproduction: anesthesia may be required to effect vaginal delivery, fetotomy Fetotomy or, should this fail, caesarean section Uterus: caesarean section.
  • Obstetric procedures used in dealing with dystocia include:
    • Mutation (correction of abnormalities of presentation, position and posture).
    • Delivery by extraction.
    • Fetotomy Fetotomy.
    • Caesarean section Uterus: caesarean section.
  • Emphasis should be placed on asepsis, adequate and repeated lubrication, rapid and thorough assessment of the problem and minimal use of traumatic instruments.
  • The presentation, position and posture of the fetus should be determined. The size and viability of the fetus, the condition of the mare's reproductive tract, and the adequacy of pelvic size are factors to consider.

Mutation

  • Depends on good restraint, lubrication, suppression of contractions and obtaining room inside the mare to maneuver, by repelling the foal out of the birth canal and into the uterus:
    • Preferably takes place with the mare in standing position (sometimes it helps to walk the mare around).
    • The use of foot or mouth snares on the foal (soft, strong cords with a loop at one end) will aid correction of many types of dystocia, when combined with repulsion.
    • Once the position, posture, etc has been corrected, delivery will often be rapid and spontaneous, sometimes proceeding without further assistance.

Traction

  • Should be applied in synchrony with the efforts of the mare by no more than two assistants, with the mare lying down and a good hold for the people pulling. Loops of obstetric ropes or chains should only be placed around the foal's pastern. In the US, two loops are used - one above the fetlock and one below the fetlock:
    • Whether using the hand or rope, traction should always be in a physiological manner. The direction of pull should be aimed downwards towards the mare's hocks once the foal's head is clear of the pelvis.
    • Where traction is applied to limbs, alternate application of traction between limbs, in unison with the mare's straining efforts, and maintain head alignment in the birth canal.
    • If the mare is standing for the final part of the delivery, ensure that there is assistance to support the foal and prevent it from falling to the ground (which could damage the foal and cause the umbilicus to rupture abruptly, before blood has been transferred through it from the placenta to the foal).

Fetotomy Fetotomy

  • Partial fetotomy is frequently used in cases of dystocia in the mare, to resolve abnormal posture in cases of an already dead foal.
  • Total fetotomy is occasionally used in the mare.

Caesarean section Uterus: caesarean section

  • Caesarean section should be opted for early on to facilitate the chances of a live foal.
  • The long-term breeding success of the mare is best protected by opting early for a caesarean section, rather than prolonged and ineffective traction or attempts at fetotomy, both of which can → damage of the cervix.

Maternal dystocia

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Malpresentation

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Malposition

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Malposture

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Fetotomy

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Newcombe J E & Kelly G M M (2014) Five cases of consecutive posterior (caudal) presentation of the fetus in two mares. Vet Rec 175 (5), 120 PubMed.
  • Pynn O (2014) Managing mare dystocia in the field. In Pract 36 (7), 347-354 In Practice.
  • Maaskant A et al (2010) Dystocia in Friesian mares: Prevalence, causes and outcome following caesarean section. Equine Vet Educ 22 (4), 190-195 VetMedResource.
  • Stephenson R (2010) Correction of dystocia in a mare by foetotomy. UK Vet 15 (4), 9-13 VetMedResource
  • Lynch Norton J et al (2007) Retrospective study of dystocia in mares at a referral hospital. Equine Vet J 38 (1), 37-41 PubMed.
  • Snider T A (2007) Umbilical cord torsion and coiling as a cause of dystocia and intrauterine foal loss. Equine Vet Educ 19 (10), 531-534 VetMedResource.
  • Byron C R, Embertson R M et al (2003)  Dystocia in a referral hospital setting: approach and results. Equine Vet J 35 (1), 82-85 PubMed.
  • McGladdery A (2001) Dystocia and postpartum complications in the mare. In Pract 23 (2), 74 VetMedResource.
  • Frazer G S, Perkins N R & Embertson R M (1999) Normal parturition and evaluation of the mare in dystocia. Equine Vet Educ 11 (1), 41-46 VetMedResource.
  • Frazer G S, Perkins N R & Embertson R M (1999) Correction of equine dystocia. Equine Vet Educ 11 (1), 48-53 VetMedResource.
  • Vandeplassche M (1980) Obstetrician's view of the physiology of equine parturition and dystocia. Equine Vet J 12 (2), 45-49 PubMed.

Other sources of information

  • Goavaere J, Martens K & de Kruif A (2013) Eds. Foal in Mare: Insights into the Foaling Mare (DVD). 4th edn. Ghent University, Belgium. Website: www.foalinmare.com.
  • Frazer G S (2004) Assessment of a Dystocia Case. In: Proc 43rd BEVA Congress. Equine Vet J Ltd, Newmarket. pp 224.
  • Emberston R M (2003) Dystocia Management. In: Proc 49th AAEP Convention. pp 6-7.
  • Jackson P G G (1995) Handbook of Veterinary Obstetrics. W B Saunders, UK.
  • Allen W E (1988) Fertility and Obstetrics in the Horse. Blackwell Scientific Publications.
  • Arthur G H, Noakes D E & Pearson H (1983) Veterinary Reproduction and Obstetrics. 4th edn. Balliere Tindall, UK.
  • Rossdale P D & Ricketts S W (1980) Equine Stud Farm Medicine. 2nd edn. Balliere Tindall, UK.


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