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.