Retained Placenta in Horses

Key takeaways

Retained placenta is a common postpartum complication in mares in which the placenta is not expelled within 3 hours of delivering a foal.

  • The exact cause of retained placenta is unknown
  • It is most common in cases of dystocia, short or prolonged gestation, abortion, and in draft mares
  • Retained fetal membranes degenerate rapidly, leading to bacterial overgrowth and toxin production
  • Bacteria and toxins from retained fetal membranes can cause serious and even life-threatening complications, such as endometriosis, metritis, laminitis, and endotoxemia
  • Diagnosis is by examination and/or transrectal ultrasonography
  • Treatment typically involves uterine lavage, administration of oxytocin, antibiotics, and anti-inflammatories, and laminitis preventive methods such as cold-hosing or icing the feet
  • Prognosis is good with prompt, appropriate treatment and in the absence of serious complications
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A closer look: Retained Placenta in Horses

This condition is one of the most common postpartum complications in mares.

Draft mares and mares with dystocia or prolonged pregnancy are particularly predisposed to placental retention.

Prolonged retention can have serious and even life-threatening complications, such as endometriosis, metritis, laminitis, and endotoxemia. Immediate veterinary attention is warranted.

When treated correctly and promptly, retained placenta has a very good prognosis. The prognosis is more guarded in cases where complications develop.

Risk factors

As a retained placenta degenerates in the mare’s body, bacterial overgrowth and toxin production begin to occur. The longer the membranes are retained, the greater the risk of complications, so time is of the essence in treating this condition.

Certain symptoms can indicate that complications may be developing.

Possible causes

The specific cause of placental retention is unknown, but risk factors include:

  • Dystocia
  • Placentitis (inflammation of the placental tissues)
  • Abortion
  • Uterine atony (poor uterine contraction)
  • Advanced age of the mare
  • Short or prolonged gestation
  • Infection

It is also more common in draft mares, particularly Friesians.

Main symptoms

The main symptom is absent or incomplete expulsion of the placenta within 3 hours of giving birth.

Testing and diagnosis

Placental tissue is considered retained when it is not expelled within 3 hours of delivery, so diagnosis is simply by observation. Veterinarians typically inspect any expelled membranes for completeness, as sometimes only parts of the placenta are retained and might not be obvious. Transrectal ultrasound of the uterus might also be necessary to identify any retained tissue.

Steps to Recovery

In the first 8 hours after birth, treatment is typically conservative and consists of the administration of oxytocin to stimulate uterine contractions and facilitate placental expulsion. After 8 hours with no passed placenta, treatment becomes progressively more aggressive.

Possible techniques include:

  • Uterine lavage
  • Antibiotics (oral or intrauterine)
  • Anti-inflammatories
  • Laminitis prevention methods, such as cold-hosing or icing the feet

Manual removal of the fetal membranes is usually avoided, as it comes with the risk of uterine damage, hemorrhage, and prolapse.

The prognosis is generally good when the condition is treated correctly and early. Cases that develop severe complications have a guarded prognosis. Mares can usually rebreed on the next cycle.


The condition is not contagious.

Prevention proves difficult, as the main cause is unknown. Recognizing a retained placenta early allows for prompt intervention and can prevent complications.

Is Retained Placenta in Horses common?

Retained placenta is a common condition in mares, especially in draft mares and mares experiencing dystocia or prolonged pregnancies.

Typical Treatment

  • Administration of oxytocin
  • Uterine lavage
  • Antibiotics (intrauterine or oral)
  • Anti-inflammatories
  • Laminitis prevention methods such as cold-hosing or icing the feet

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