Retained Placenta in Horses: Post-Foaling Emergency in Mares

Retained placenta, also called retained fetal membranes, means the mare has not fully expelled the placenta after foaling. In mares, this is generally considered abnormal if the membranes are still present more than 3 hours after birth. That short timeline matters because horses are much more prone than many other species to dangerous complications after placental retention.

This is a true postpartum emergency. A mare with retained placenta can develop uterine infection (metritis), endotoxemia, fever, depression, colic signs, and laminitis. In some cases, only a small portion of the placenta remains inside the uterus, so the problem may be less obvious than a large sheet of membranes hanging from the vulva.

After every foaling, the placenta should be saved and examined to make sure it is complete. If any part appears missing, especially the tip of the nongravid horn, your vet should be contacted right away. Early treatment often improves the mare's comfort and lowers the risk of life-threatening complications.

The exact cause is not always clear. In many mares, retained placenta happens without one single obvious trigger. What matters most is recognizing that the membranes should normally pass quickly after foaling, and delayed passage raises concern even if the mare looked normal during labor.

Risk appears to be higher after dystocia, difficult delivery, traumatic uterine manipulation, abortion, stillbirth, cesarean delivery, or illness around foaling. Mares with inflammation or damage in the uterus may also have trouble separating and expelling the membranes normally.

Sometimes the entire placenta is retained. In other cases, only a small section remains, often from the nongravid horn, and that can be easy to miss. Because even a small retained piece can trigger infection and endotoxin release, your vet may recommend treatment and monitoring even when the mare seems stable at first.

Diagnosis often starts with timing and observation. If the placenta has not passed within 3 hours after foaling, your vet will treat that as retained placenta. If the placenta did pass, your vet may still suspect a retained piece if the membranes look incomplete when examined or if the mare later develops fever, discharge, colic signs, or laminitis.

Your vet may perform a postpartum physical exam, assess the mare's temperature, heart rate, hydration, gum color, and comfort, and inspect the vulva and uterus. In some cases, a careful manual exam and ultrasound help identify retained tissue, uterine fluid, or postpartum complications such as metritis.

Bloodwork may be recommended if the mare looks systemically ill or if your vet is concerned about infection, inflammation, or endotoxemia. Diagnosis is not only about confirming retained tissue. It is also about checking how sick the mare is, whether the uterus is clearing normally, and whether the feet need aggressive laminitis prevention.

Not every case can be prevented, but careful foaling management can lower risk and help your vet intervene earlier. Good late-gestation broodmare care, a clean foaling environment, and prompt attention to dystocia or abnormal labor all support a safer postpartum period.

After foaling, watch the mare closely and note the exact time the foal was delivered. The placenta should be passed within 3 hours. Save it, lay it out in an F-shape if possible, and check whether it appears complete. If membranes are hanging from the vulva, do not pull on them and do not remove them without veterinary guidance.

Mares that had a difficult birth, uterine manipulation, abortion, stillbirth, or other postpartum complications deserve especially close monitoring. Taking the mare's temperature, watching for discharge or colic signs, and checking for early foot soreness can help catch trouble sooner. Prevention in practice is often about rapid recognition and early veterinary care, not waiting to see if the problem resolves on its own.