The time around foaling (periparturient period) is a high-risk period for mares, as their bodies undergo many changes associated with delivery of the foal. Breeders must closely monitor their mares for signs of medical emergencies before, during, and after foaling.

One of the most common periparturient emergencies is dystocia, or difficulty giving birth. Retained placenta (fetal membranes) is also common after delivery, and can quickly lead to laminitis.

This article will focus on other less common emergencies that require immediate veterinary intervention for the safety of the mare and the foal. Examples include periparturient hemorrhage, postpartum colic, and uterine prolapse.

When caring for a pregnant mare, preparation, emergency planning and good communication with your veterinarian are key. Continue reading to learn more about reproductive emergencies in mares, their signs, and general approaches to management.

Reproductive Emergencies in Mares

Broodmares require careful management and monitoring due to the potential for reproductive emergencies, which can arise during breeding, pregnancy, and foaling. The risk of complication is especially high during the periparturient period.

The periparturient period refers to the time surrounding parturition, or the birthing process. In mares, this period typically encompasses the weeks immediately before and after foaling.

It is a critical phase for both the mare and the foal, characterized by significant physiological changes in preparation for birth and the onset of lactation.

During the periparturient period, mares can be at risk for various complications, including:

  • Dystocia (difficult birth)
  • Retained fetal membranes
  • Periparturient hemorrhage
  • Prepubic tendon rupture
  • Postpartum colic
  • Hydropsical conditions
  • Uterine prolapse
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Periparturient Hemorrhage

Periparturient hemorrhage is a potentially life-threatening condition characterized by excessive bleeding that occurs around the time of parturition, often due to the rupture of a major blood vessel. Prompt veterinary intervention is crucial to manage the bleeding and stabilize the mare’s condition.

There are several arteries within close proximity to the reproductive tract that may become compromised due to the physical, hormonal, and physiological changes associated with delivery. Studies show that around 2-3% of broodmares will experience periparturient hemorrhage from one of these arteries, often resulting in death of the mare. [1]

The artery that most commonly ruptures is the right uterine artery, which runs along the upper surface of the right uterine horn. [1] It is thought that the right uterine artery is predisposed to rupture due to its location adjacent to the cecum, which may compress the artery and increase blood pressure locally. [1]

Risk Factors

The exact cause of periparturient hemorrhage in pregnant mares is unknown. Possible risk factors include: [1][2]

  • Aging mares with weaker vessel walls
  • Multiparous mares (mares that have had multiple foals)
  • Copper deficiency resulting in abnormal vessel wall elasticity

Symptoms

The main symptom of periparturient hemorrhage is vague colic signs, such as restlessness and pawing at the ground. [1] Typically, the artery bleeds into tissues surrounding the uterus, so no obvious external bleeding is present. [1]

Symptoms of periparturient hemorrhage may include:

  • Flank watching
  • Rolling
  • Flehmen response

The Flehmen response involves the horse curling back its upper lip, exposing its front teeth, and inhaling.

Severe Blood Loss

In cases where the bleed overwhelms the tissues surrounding the uterus, the mare may experience blood loss into her abdominal cavity. Symptoms of severe bleeds include: [1][3]

  • Rapid heart rate
  • Weakness
  • Muscle tremors
  • Sweating
  • Pale gums
  • Cool extremities

Diagnosis

Since there is no obvious external bleeding in mares with periparturient hemorrhage, veterinary expertise is required to make a diagnosis.

Diagnostic tests may include:

  • Ultrasound of the abdomen to identify fluid
  • Rectal palpation to identify any blood clotting or fluid in the tissues
  • Abdominocentesis, or sampling of abdominal fluid
  • Bloodwork showing low red blood cell percentage (hematocrit) and high lactate levels

Treatment and Prognosis

Despite the absence of visible bleeding, affected mares still experiencing significant blood loss internally. Treatment focuses on maintaining blood volume and encouraging blood clotting to stop the bleed.

Treatments for periparturient hemorrhage may include: [1][3]

  • Intravenous fluid therapy
  • Blood transfusions
  • Pain control, such as flunixin meglumine
  • Medications that promote blood clotting, such as aminocaproic acid

During treatment, mares must be kept as calm as possible. Stress or excitement can increase the mare’s blood pressure, disrupting any blood clots that have formed or exacerbating a current bleed. [3] For these reasons, many veterinarians will sedate the mare to reduce her stress.

Overall, mares with periparturient hemorrhage have an 84% survival rate with appropriate, prompt treatment. [1] In surviving mares, the blood clot that forms will gradually reduce in size over time. These mares are often able to successfully conceive and deliver foals without subsequent hemorrhage episodes. [3]

In very severe cases, large clots may not reduce completely and instead form scar tissue that can prevent future pregnancies in the mare. [3]

Prepubic Tendon and Abdominal Wall Rupture

During pregnancy, the mare’s abdomen must expand greatly to accommodate both her internal organs and the growing foal. The shape of the abdomen is primarily maintained by the prepubic tendon, which runs from the pelvis to the midline of the abdomen. [1]

In the last two months of gestation, the prepubic tendon experiences a large amount of strain, and can rupture. This results in severe enlargement or distension of the abdomen, as the unsupported abdominal organs sink lower to the ground. [1]

If left untreated, there is a risk of complete evisceration, which means that the mare’s internal organs could spill out through a tear in the skin and abdominal wall muscles. [1] This is a life-threatening condition that requires immediate veterinary surgical intervention.

Risk Factors

The primary risk factor for prepubic tendon rupture is excessive uterine weight, either due to foal size or accumulation of fluid. The main causes of excessive weight include: [1]

  • Hydropsical conditions (described later)
  • Twins
  • Overly large foals

Factors that weaken the prepubic tendon can also increase the risk of rupture. These risk factors include:

Symptoms

The initial symptom of an impending prepubic tendon rupture is swelling of the lower abdomen. Typically, the swelling is edematous, which means that it is caused by an accumulation of fluid in the tissues. The swelling also exhibits “pitting,” such that when the tissue is pressed, an indentation remains. [1][3]

The swelling can be extremely painful for the mare. Additional symptoms that indicate prepubic tendon rupture include:

  • Lowering of the abdominal wall profile
  • Bloody or pink-tinged milk production
  • Reluctance to walk
  • Rapid heart rate
  • Colic signs
  • A “sawhorse stance”, where the mare stands with her front feet extended forward and her hind feet stretched backward

Diagnosis involves ultrasound of the abdomen to identify swelling and hemorrhage within the abdominal wall.

Treatment and Prognosis

In mild cases, proper management can result in the mare successfully delivering a foal. Management strategies include: [1]

  • Pain control, such as flunixin meglumine (banamine)
  • Stall rest
  • Abdominal support wrap

For more severe cases, Cesarean section (C-section to deliver the foal) or euthanasia of the mare are the only options. [1][4] The foal may or may not survive Cesarean section depending on the gestational length at the time of surgery. [4]

Mares that survive foaling must be retired from breeding, as their weakened prepubic tendon is at risk of catastrophic failure with a subsequent pregnancy. [1][3]

Abdominal Wall Rupture

A similar condition, abdominal wall rupture, involves weakening and tearing of the abdominal wall muscles, without compromise of the prepubic tendon. [3] This condition is less severe, and many cases result in successful foaling with appropriate management. [3]

Surgical repair of the muscle defect is necessary after the mare foals, but many mares are able to return to breeding after treatment. [3]

Postpartum Colic

Postpartum mares have a strong predisposition to large colon volvulus, in which the colon twists on itself preventing passage of feces. [1][5] This is a form of impaction colic, characterized by obstruction of the intestinal tract, causing abdominal pain and potentially serious complications.

The exact reason why postpartum mares have an increased risk of large colon volvulus is not known. However, possible explanations include: [5]

  • The increased size of the abdomen post-delivery may give the colon greater mobility, enabling it to twist.
  • An increase grain intake in the mare’s diet to support lactation could contribute to digestive upset.
  • There may be a genetic predisposition that makes certain mares more susceptible to this condition.

Thoroughbred mares have the highest risk of this condition and may have a genetic predisposition to colic after foaling. [5]

Symptoms

Horses with large colon volvulus display severe colic symptoms, such as: [5]

  • Rolling, thrashing, or unwilling to stand
  • Rapid heart rate
  • Rapid breathing
  • Bright red or blue and pale gums

If you observe these signs in your postpartum mare, contact your veterinarian immediately. A veterinarian can quickly identify the volvulus based on a rectal examination.

Treatment and Prognosis

Large colon volvulus requires surgical intervention to treat. Prompt referral to a surgical center is key for a good prognosis.

The veterinarian examining the mare may place a trochar to remove gas accumulating in the colon to help stabilize the mare for transport to the referral center. [5] Intravenous fluids, pain control, and sedation are also common components of the stabilization protocol. [5]

The prognosis is good for mares referred for colic surgery promptly after symptoms arise.

Some mares may experience repeated large colon volvulus after foaling. [5] These mares may be candidates for colopexy, where the wall of the colon is sutured to the abdominal wall to prevent the colon from rotating. [5]

Large colon volvulus does not generally affect the future fertility of the mare. [1][5]

Hydropsical Conditions

Hydropsical conditions in periparturient mares refer to two distinct but related disorders: hydrops amnion (hydramnios) and hydrops allantois (hydrops of the allantois). These conditions involve the excessive accumulation of fluid within the two fetal membranes – the amnion and the allantois – that surround the developing foal. [1]

  • Hydrops amnion (hydramnios): This is the less common of the two and involves an abnormal increase in the amniotic fluid, which is the fluid directly surrounding the fetus. It tends to develop slowly over time and may not be as immediately life-threatening. [1]
  • Hydrops allantois: This condition is more common in horses, and is characterized by an excessive buildup of allantoic fluid, which is the fluid within the allantoic sac, a part of the placenta that exchanges nutrients and waste between the mare and the foal. Hydrops allantois typically has a rapid onset and can be more dangerous due to the rapid distension of the mare’s abdomen, leading to respiratory and circulatory distress. [1]

Hydropsical conditions typically develop during the last trimester of pregnancy. If left untreated, the weight of the accumulating fluid can lead to conditions such as prepubic tendon rupture in the mare. [1]

Risk Factors

Risk factors for hydropsical conditions are not well-established. However, some proposed risk factors include: [6]

  • Genetic predisposition
  • Draft breed mares

There is some evidence to suggest that hydropsical conditions are associated with Leptospira infections. [6][7] Pregnant mares sharing pastures with horses experiencing recurrent uveitis or who had an abortion due to leptospirosis may have a higher risk of hydrops. [6]

Symptoms

The symptoms of hydropsical conditions arise from the pressure exerted by the accumulating fluid. Clinical signs include:

  • Progressively enlarging abdomen
  • Swelling and edema of the lower abdomen
  • Colic signs
  • Reduced appetite
  • Rapid heart rate

Contact your veterinarian to obtain an accurate diagnosis. Ultrasound of the abdomen can quickly identify excessive fluid and confirm the diagnosis.

Treatment and Prognosis

Unfortunately, treatment of hydropsical conditions often results in loss of the foal. The main treatment is inducing abortion in the mare, followed by careful management to ensure the foal is delivered safely. [1]

After delivery, mares with hydrops will almost always have retained fetal membranes, requiring additional treatment by the veterinarian. [1]

Studies show that 95% of mares that recover from hydrops go on to foal successfully in the future, as long as there is no significant damage to the reproductive tract or abdominal wall. [1] Some mares may develop hydrops in subsequent pregnancies. [6]

Uterine Prolapse

Uterine prolapse in mares is a serious postpartum condition where the uterus inverts and protrudes through the vaginal opening following the delivery of a foal. This condition typically occurs shortly after foaling and can be precipitated by factors such as a difficult birth and excessive straining by the mare.

Uterine prolapse occurs due to the relaxation of the mare’s ligaments and supporting structures during delivery. The relaxed structures allow the uterus more freedom to move around within the abdomen. When combined with excessive straining during delivery, this may result in the uterus everting and protruding through the mare’s vulva. [5]

As the uterus prolapses through the vulva, it causes tension on important ligaments and vessels. In some cases, vessels may rupture, resulting in significant blood loss. [5] Left untreated, continued straining by the mare can also result in prolapse of the urinary bladder. [5]

Risk Factors

Uterine prolapse is commonly associated with other reproductive conditions, such as: [5]

  • Dystocia (difficult birth)
  • Retained fetal membranes
  • Excessive administration of oxytocin
  • Colic
  • Abortion

All of these factors can cause a mare to strain excessively during foaling, resulting the uterine prolapse.

Symptoms

The main symptom of uterine prolapse is a mass of red, often bloody tissue protruding from the vulva. Investigation of the tissue by a veterinarian can identify the tissue present, and the severity of any damage that may have occurred.

Treatment and Prognosis

Treatment involves placing the uterus back into the mare’s abdomen. The veterinarian will administer sedation to keep the mare calm, and may perform an epidural block to numb the area and to reduce tissue contractions. [5][8]

The protruding tissue is thoroughly washed to remove any contamination and reduce the risk of infection. [5][8]

To replace the uterus, the veterinarian elevates the uterus to a level above the vulva, then carefully massages the tissue back inside. [5][8] Once the uterus is back within the abdomen, the veterinarian can distend the uterus with sterile fluid to ensure that all parts of the uterus return to their normal position. [8] Some veterinarians may include antibiotics in this fluid to reduce the risk of infection. [8]

Continued treatment often involves fluid therapy to correct calcium imbalances and low doses of oxytocin to maintain uterine tone. [2] Some mares may require sutures to prevent repeated prolapse. [2] Most mares with uterine prolapse also experience retained fetal membranes, requiring additional treatment by the veterinarian.

Most mares make a full recovery from uterine prolapse, however their future fertility may be compromised if there is significant damage to the uterine wall. [8] Mares that are treated promptly have the best chance of maintaining fertility. [8]

Summary

  • The periparturient period is a high-risk period for mares where they are at risk of several medical emergencies
  • The most common periparturient emergencies are dystocia and retained fetal membranes
  • Less common emergencies include periparturient hemorrhage, uterine prolapse, hydropsical conditions, prepubic tendon rupture, and large colon volvulus
  • Work closely with your veterinarian to prepare an emergency plan in case of reproductive emergencies

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References

  1. Slovis, N. and Irvin, L., Neonates and Periparturient Mares. Veterinary Clinics of North America: Equine Practice. 2023. View Summary
  2. Frazer, G. S., Postpartum Complications in the Mare. Part 1: Conditions Affecting the Uterus. Equine Veterinary Education. 2002.
  3. Brinsko. S. P. and Blanchard. T. L., Eds.Manual of Equine Reproduction, 3rd edition. St. Louis, Mo: Mosby/Elsevier. 2011.
  4. Reed, S. M. et al., Equine internal medicine, 3rd ed. Saunders Elsevier, 2010.
  5. Lu, K. G. and Sprayberry, K. A., Managing Reproduction Emergencies in the Field: Part 2: Parturient and Periparturient Conditions. Veterinary Clinics of North America: Equine Practice. 2021. View Summary
  6. Diel de Amorim, M. et al., Treatment of Hydropsical Conditions Using Transcervical Gradual Fetal Fluid Drainage in Mares With or Without Concurrent Abdominal Wall Disease. Journal of Equine Veterinary Science. 2018. View Summary
  7. Shanahan, L. M. and Slovis, N. M., Leptospira Interrogans Associated with Hydrallantois in 2 Pluriparous Thoroughbred Mares: Leptospira Interrogans Associated with Equine Hydrallantois. J Vet Intern Med. 2011.
  8. Crabtree, J., Peripartum Problems in Mares 2. Postpartum Problems. In Practice. 2012.