Postpartum complications in mares occur in a relatively low percentage of cases. Often these complications are serious, or even lethal. Although assisted parturition is good practice and may prevent some of these complications, often these complications will occur despite human intervention. Assisted parturition has the advantage that these complications are noticed during, or soon after, birth and can therefore be addressed soonest.
The postpartum complications below are the most commonly encountered complications where veterinary input is required.
Vaginal trauma is generally the result of either a foal delivered in an abnormal position, or where the foal is in a normal position but oversized for passage through the pelvic canal. This can lead to intrapelvic peri-vaginal bleeding, resulting in haematoma formation. Large haematomas can be drained two to three days postpartum, after clot formation has occurred.
If haematomas do not regress or do not become progressively firm, abscessation should be suspected. Abscesses should be incised and drained as long as they are retroperitoneal. These structures can be easily diagnosed through vaginal ultrasonography. Occasionally, large haematomas can leave permanent lumps of scar tissue that are palpable in the pelvic canal.
In cases of dystocia, severe disruption of the mucosa of the vagina can lead to infection and can often result in the formation of scar tissue. This scar tissue contracts and can lead to deformity and even narrowing of the vaginal cavity. The contraction of the scar tissue can disrupt the normal functioning of the cervix, leading to future conception failures and abortions.
Cervical lacerations are most commonly sustained during parturition. They may be associated with dystocia or induced parturition but can also occur with normal births. Assisted vaginal delivery and inadequate lubrication can increase the risk of a cervical tear.
Haemorrhage from the middle uterine, utero-ovarian or external iliac arteries is a significant cause of peripartum colic syndrome and death. This can occur prior to parturition, during parturition or postpartum. It can present as a subtle or profound condition depending on the severity of the blood loss and the location of blood loss (abdominal, broad ligament, into the uterus or uterus wall). The clinical presentation may vary from haemorrhagic shock, abdominal pain and colic symptoms and weakness. Mares are normally depressed with pale mucous membranes and an elevated heart rate of around 80bpm.
Rectal tears as a spontaneous postpartum complication is fortunately not a common condition. These tears are normally as a result of dystocia and assisted parturition. Rectal tears immediately after parturition, without dystocia, are usually Grade IV tears (all the layers of the rectum) and can be associated with prolapse of small colon or small intestine through the tear and the anus. These tears lead to faecal contamination of the abdomen with peritonitis and death.
Recto-vaginal fistula is a relatively common injury sustained during parturition. Fistulas most commonly occur secondary to dystocia and are normally caused by the foal’s nose or foot being forced through the dorsal vaginal wall into the rectum. Spontaneous retraction or manual replacement of the foal’s head or extremity into the correct position limits the injury to a recto-vaginal fistula.
If parturition proceeds before correction, the result is usually a third-degree perineal laceration. These lacerations are corrected surgically once complete healing of the wounds have taken place. Although such a laceration appears serious to the owner, it is not an emergency. Faeces may drop into the vagina during defecation, often leading to a mild vaginitis.
Uterine prolapse is an uncommon complication in the postpartum mare but must be considered and dealt with as a life-threatening emergency. The most common causes of uterine prolapse are dystocia, retained placenta and abortion. Diagnosis of uterine prolapse is quite straightforward and the uterus may extend all the way to the ground.
The uterus is suspended in the abdominal cavity by the broad ligament, which derives its attachment from the lateral sub-lumbar and pelvic walls. The arteries, veins, lymphatic vessels and loose collagenous and adipose tissue, together with smooth muscle continuous with the outer layer of the uterine tube and uterus, are contained between the two layers of the broad ligament, which becomes continuous with the lateral ligaments of the bladder.
During uterine prolapse, tearing of the arteries is possible. Due to the position of the prolapsed uterus and severe oedema, these torn arteries may be clamped with no immediate bleeding. Once the uterus is reduced and replaced, these arteries may start bleeding, either into the broad ligament, or freely into the abdominal cavity. The practitioner should keep in mind that prolapse of the bladder should also be considered with uterine prolapse.
Retained placenta is considered the most common postpartum complication in mares. A placenta is considered retained if it has not been expelled by three hours postpartum. Retained placenta tends to be more associated with abortion, dystocia, stillbirths and twinning.
The most obvious sign of retained placenta is the appearance of tissue protruding from the vulva. It may range from slightly visible to dragging on the ground. Often no placental tissue is visible due to tearing of the placenta with only part of it still retained in the uterus. Placentas protruding from the vulva and touching the hocks should be tied up away from the hocks. This prevents the mare stepping onto the placenta causing it to tear. This will also reduce the risk of the mare kicking at the placenta, and in doing so, possibly injuring the foal.
Bacterial endometritis is a significant problem in the mare postpartum. Postpartum endometritis often occurs for the following reasons:
- Unhygienic conditions in which the mare foals down
- Retained placenta
- Uterine bleeding and pooling of blood in the uterus due to delayed involution
- Older mares with poor uterine tone and pooling of fluids after parturition
- Tearing of the vulva during parturition and the aspiration of air and faecal material up the vagina
The practitioner must be aware of these factors which can initiate endometritis. Addressing these factors will prevent postpartum endometritis in the majority of cases.
Rectal impaction/hind limb paresis
This is a condition observed occasionally, especially in older mares. During the foaling process, pressure on the lumbar/sacral back region and potential damage to the ischiatic nerves may cause either paralysis or paresis, with rectal impaction.