Mare Abortion Signs: Warning Symptoms Before or After Pregnancy Loss

Pregnancy loss in mares can happen for infectious or noninfectious reasons, and the warning signs are not always dramatic. According to Merck Veterinary Manual, the most common noninfectious cause of abortion is twinning, while important infectious causes include placentitis and equine herpesvirus-1 (EHV-1). In many cases, the first visible clue is only premature mammary gland or udder development. Some mares also develop vulvar discharge, especially with placentitis.

Placentitis is one of the most important causes because it may start quietly and then progress to abortion, stillbirth, or a weak foal. Cornell notes that placentitis is a leading cause of abortion and neonatal infection in mares. Bacterial or fungal infection of the placenta can trigger inflammation, discharge, premature lactation, and fetal compromise.

Other recognized causes include umbilical cord abnormalities, congenital fetal problems, and fescue toxicosis in mares grazing endophyte-infected tall fescue. Merck also notes that EHV-1 abortions usually happen in the last trimester and mares often show little or no warning illness beforehand. Equine viral arteritis can also cause abortion, and unlike EHV-1, some mares may show signs of systemic illness before the loss.

Early pregnancy loss can be especially frustrating because the cause is often never identified. Cornell reports that in many early losses, no clear underlying cause is found. That is one reason your vet may recommend saving the fetus, placenta, and any discharge for testing instead of discarding them.

See your vet immediately if your mare passes a fetus, has red or brown vaginal discharge, develops premature udder filling, spikes a fever, seems depressed, has colic-like signs, or shows a foul-smelling discharge after abortion. These signs can point to placentitis, active pregnancy loss, retained fetal membranes, uterine infection, or systemic illness. If an infectious cause such as EHV-1 or equine viral arteritis is possible, quick isolation matters for herd protection too.

Pregnant mares are not good candidates for a wait-and-see approach when reproductive signs appear. Merck notes that mares aborting from EHV-1 often have few or no premonitory signs, so even mild changes deserve attention. A mare that seems outwardly stable may still have a compromised fetus, placental disease, or retained tissue.

After a loss, monitoring at home is limited to supportive observation while you are already arranging veterinary care. Watch for fever, reduced appetite, depression, laminitis stance, continued straining, or membranes still present. Merck advises that fetal membranes should normally pass within 3 hours after birth, and retained membranes can lead to endotoxemia, laminitis, and death if not treated promptly.

Until your vet arrives, separate the mare from other horses, prevent dogs or wildlife from contacting fetal tissues, and handle all materials with gloves. Cornell specifically advises keeping aborted fetuses and placentas away from other animals and contacting your vet with any reproductive disease concern.

Your vet will usually start with a physical exam, temperature, heart rate, and reproductive history, including breeding dates and how far along the mare is. A transrectal and/or transabdominal ultrasound is often the fastest way to assess fetal heartbeat, placental thickness, fluid quality, twin pregnancy, and whether any fetal or placental tissue remains in the uterus.

Testing may include a vaginal exam, bloodwork, and sampling of the fetus, placenta, or discharge for culture, PCR, or pathology. If EHV-1 is a concern, Merck notes that abortion material, placentas, placental fluids, and nasal secretions can spread infection, so your vet may recommend strict biosecurity and herd-level precautions. If the mare aborted because of EHV-1, future fertility is often preserved, but identifying the cause still matters for management and prevention.

If the mare is still pregnant but placentitis is suspected, your vet may discuss treatment options aimed at prolonging pregnancy and supporting the fetus. If the abortion has already happened, care focuses on the mare: checking for retained placenta, uterine infection, dehydration, endotoxemia, pain, and laminitis risk. Merck warns that retained membranes in mares can become life-threatening and should never be manually pulled by the pet parent.

Depending on findings, your vet may recommend oxytocin, anti-inflammatory medication, antimicrobials, IV fluids, hoof monitoring, and follow-up ultrasound. In some cases, referral to an equine hospital is the safest option, especially if the mare is systemically ill, has severe retained membranes, or needs intensive monitoring.

Home care starts with biosecurity and observation, not home treatment alone. Move the mare away from pregnant mares and shared nose-to-nose contact if possible. Wear gloves, bag fetal tissues and placenta if your vet wants them submitted, and keep dogs, cats, and wildlife away from the area. Save the placenta intact if you can, because it can provide important clues about placentitis, twins, or cord problems.

Keep the mare in a quiet, clean area with fresh water and easy access to hay unless your vet gives different instructions. Check her temperature, appetite, manure output, comfort, and whether she is passing any membranes or abnormal discharge. Do not pull on tissue hanging from the vulva. Merck specifically warns that manually pulling retained placenta can damage the uterus or leave pieces behind.

Watch closely for worsening signs such as fever, depression, foul odor, continued straining, swollen feet, reluctance to move, or a rocked-back stance that could suggest laminitis. Those changes mean your vet needs an update right away. If your mare was grazing tall fescue and is late in gestation, mention that history because fescue toxicosis can affect pregnancy and lactation.

Emotionally, pregnancy loss can be hard on the whole barn team. It helps to focus on practical next steps: protect the mare, protect the herd, document what you saw, and follow your vet’s recheck plan. Many mares recover well physically with prompt care, even when the cause of the loss is never fully confirmed.