Dystocia - Horse
Introduction
Dystocia refers to abnormal or difficult birth. It is a potentially dangerous condition for mare and foal and must be treated as an emergency if it occurs.
Dystocia is mainly due to abnormal foetal presentation, position or posture. Foetal oversize and maternal factors such as uterine inertia or narrowed pelvic canal can sometimes be the cause.
The incidence is thought to be 4% in thoroughbreds, 10% in Belgian draught horses due to foetal muscular hypertrophy, and 8% in Shetland ponies due to the large skull.
Clinical approach to dystocia
Assessment of mare
Dystocia should be suspected if first stage labour is very prolonged or if delivery of the foal does not follow within 20-30 minutes of rupture of the foetal membranes and release of foetal fluids.
The mare should be rapidly assessed for signs of shock or haemorrhage and a capsule history should be obtained, including length of gestation, mammary development, concurrent problems and recent developments.
The best place to examine the mare is in a large straw-bedded box. Depending on the mare's condition, sedation may be necessary. Acepromazine does not affect the foetus but may not have appropriate sedative effects. Xylazine and detomidine do affect foetal cardiovascular parameters and xyalizine, if necessary, is preferred due to its shorted duration of action.
Epidural administration of lidocaine and xylazine can reduce straining and provide perineal analgesia. Potential problems include maternal hindlimb weakness and ataxia which might prevent transport to a different facility.
Obstetric manipulation
The type of abnormality should be determined through vaginal examination.
The foal's viability should be assessed as management will vary depending on whether the foal is alive or dead.
Copious amounts of lubrication should be used and lubricant can be pumped into the uterus via a nasogastric tube if necessary.
Different manipulations including repulsion, traction, extension of limbs and use of ropes may be necessary to correct the foal's position
Posterior presentation of the foal is extremely rare and foal death rates are high due to asphyxia from compression or early severance of the cord.
Decision-making
Foetotomy: The main aim is to save the mare's life and future breeding potential if the foal has died. Great care must be taken not to traumatise the birth canal. Although this technique is still favoured in some regions, it has largely been superceded by caesarean section which has a lower incidence of complications.
Caesarean: This should be considered if no progress is being made by vaginal manipulation after 15-20 minutes. It will also depend on the proximity of hospital and foal intensive care facilities. On-farm anaesthesia and surgery may be the only option. This is usually done in a standing mare via a low left flank approach.
Post-partum complications
Mares with dystocia are more likely to develop post-partum complications including:
- Retained placenta: treated by manual removal or oxytocin in an intravenous drip or through intramuscular boluses.
- Metritis: which can lead to toxaemia and laminitis and should be treated aggressively.
- Intestinal problems: ileus or constipation, intestinal rupture, rectal prolapse
- Uterine prolapse
- Cervical tears
- Uterine rupture
- Uterine Haemorrhage
- Perineal lacerations
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References
Noakes, D. (2001) Arthur's veterinary reproduction and obstetrics Elsevier Health Sciences
McGladdery, A. (2001) Dystocia and postpartum complications in the mare In Practice 23:74-80