Horse-Breeding Issues: Retained Placenta

Determine your course of action in the event that your broodmare retains her placenta after foaling.

One of the most common problems that can occur after a broodmare foals is retention of the placenta. Between 2 and 10 percent of broodmares are estimated to retain their placenta, which should be considered a true emergency that requires the attention of a veterinarian. The placenta is the sac-like membrane that lines the mare’s uterus. It receives nutrients from the uterus and passes them along to the fetus via the umbilical cord. Because the placenta normally is expelled 30 minutes to three hours after birth, most veterinarians consider the placenta to be retained after if it is still present at least two or three hours after foaling. A placenta that is retained for an extended period of time – greater than six to eight hours – might cause serious uterine infection, toxemia, laminitis (founder) and even death.

Possible Causes

Factors that predispose a mare to retaining her placenta include induction of parturition (foaling) before all signs of impending foaling are present, eating fungus-infected fescue grass or hay, foaling difficulties that require intervention and fatigue of the uterus following prolonged labor. For some unexplained reason, placental retention is more common in mares that are members of draft breeds than in Quarter Horse, Thoroughbred or Standardbred mares. In most cases, a portion of the placenta will be exposed. However, it is critical that the placenta is never pulled in an attempt at removal. Forcible traction can cause permanent damage to the uterine lining (endometrium), hemorrhaging, infertility or prolapse of the mare’s uterus. The latter is life-threatening.

Before and After the Vet Arrives

While waiting for the veterinarian to arrive, it’s a good idea to tie the exposed portion of the placenta itself above the mare’s hocks with a piece of string or twine, or knot the placenta on itself. This prevents the retained placenta from hitting the mare’s lower legs, which can upset nervous mares, and prevents the mare from stepping on it. The added bulk from the knot actually might aid the mare in passing the placenta.

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Once the veterinarian arrives, one or a combination of several therapeutic treatments might be used to remove placental membranes. These include injections of oxytocin, infusing the uterus with a warm solution and manual separation. Oxytocin stimulates the uterus to contract, which usually causes the placenta to separate and be expelled. This can be administered by intramuscular injection or mixed with a liter of saline and slowly administered intravenously over 30 to 40 minutes. Most mares will expel the placenta within 15 to 20 minutes following this treatment. Occasionally,mares require several oxytocin injections administered at two-hour intervals. A second technique frequently used to expel the placenta is to infuse three to four gallons of warm betadine-saline solution (diluted 1:10) into the mare’s uterus. The large volume of warm fluid distends the uterus and allows the uterine crypts to release the placental villi. Membranes are then usually passed within five to 30 minutes. The advantage of both of these techniques is that the uterus is not invaded, thus reducing the risk of uterine contamination and infection. Combining both techniques is not uncommon. Some clinicians still manually separate the placenta from the uterus. When performed carefully, this technique is effective, but there is always an increased chance of infection, hemorrhage or damage to the uterine lining. If the fetal membranes have been retained for more than three to six hours, antibiotics and anti-inflammatory drugs are also administered, especially in protracted cases or in cases where severe uterine contamination is suspected. In placenta retained more than eight hours, bacteria multiply rapidly. The bacteria not only might cause severe uterine contamination but can produce potent toxins that cause fever, laminitis and even death.

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Anti-inflammatory drugs that most commonly are used are flunixin meglumine or phenylbutazone, which aid in preventing laminitis and also eliminate colic that could occur after removal of the placenta. Broad-spectrum antibiotics that are used to control or prevent infection can be administered in solution directly into the uterus or administered systematically as an intramuscular or intravenous injection.

Examining the Placenta

After the placenta is expelled, it should be carefully examined to ensure that all of it is present. Retaining even a small piece of placenta can result in the problems discussed earlier. To examine the placenta, the veterinarian will lay it on a clean surface and evaluate it for completeness. If he doubts the membranes are complete, they can be filled with water through the single hole produced by the foal’s birth. An intact placenta, which is balloon-like, will hold the water. If the examination determines that a portion of the placenta remains in the mare’s uterus, flushing with antibiotics solutions can be used to remove it. Following espulsion of the retained placenta, most mares experience delayed uterine involution (return of the uterus to its normal size) and, therefore, are not fertile on their foal heats. If these mares are bred on their foal heats, they might become pregnant, but often they will experience fetal loss early in pregnancy. Retention of the placenta for more than two to three hours indicates a true emergency. If your mare retains her placenta or you have questions about placental retention, contact a veterinarian immediately.

AQHA Video

Check out "Newborn Foal Care," an AQHA video designed to educate foal owners on how to care for your foal in his first hours of life.