Uterine Torsion in Horses: Pregnancy-Related Colic Emergency in Mares

Uterine torsion is a twist of the pregnant uterus around its long axis. In mares, this is an uncommon but serious cause of abdominal pain during pregnancy, most often in the second half of gestation and especially in the last trimester. Because the equine uterus is suspended by broad ligaments, a twist can tighten those supporting tissues and interfere with normal blood flow to the uterus and placenta.

For some mares, the first sign looks like ordinary colic. The pain may be mild, intermittent, and easy to mistake for a gastrointestinal problem. That is one reason uterine torsion can be dangerous: a mare may not look dramatically ill at first, even though the pregnancy is at risk.

As the torsion worsens or lasts longer, the mare can become more painful, the uterus can become compromised, and the foal may lose oxygen or die. In severe cases, tissue damage, uterine rupture, shock, or loss of both mare and foal can occur. Early recognition and rapid veterinary care give the best chance of a good outcome.

In many mares, there is no single clear cause. Uterine torsion is thought to happen when the heavy pregnant uterus rotates within the abdomen. It is reported most often in mid- to late gestation, when the uterus is larger and more mobile. The exact trigger may never be identified in an individual case.

Possible contributing factors include fetal movement, the mare rising or rolling, changes in abdominal space late in pregnancy, and individual anatomy of the uterus and broad ligaments. Unlike some other species, mares often do not have obvious vaginal involvement, which is why the problem can be harder to detect on a routine external exam.

It is important not to blame yourself if this happens. Good management does not eliminate all risk. Uterine torsion is considered an uncommon reproductive emergency, and even attentive pet parents may only notice vague colic signs at first.

Your vet usually starts with an emergency colic exam and pregnancy-focused reproductive exam. In mares, the most important clue is often found on rectal palpation, where your vet may feel one or both broad ligaments stretched abnormally across the uterus. This helps identify the direction and likely degree of the twist.

Transrectal ultrasound may be used to assess the uterus, placenta, fetal viability, and other reproductive structures. Your vet may also check heart rate, hydration, mucous membranes, pain level, and bloodwork to understand how stable the mare is and whether referral is needed.

Because pregnant mares can colic for gastrointestinal reasons too, diagnosis often includes ruling out intestinal disease. A vaginal exam may be less helpful in mares than in cattle because the torsion often occurs in front of the cervix. If uterine torsion is strongly suspected, rapid referral to an equine hospital is often recommended so the mare can be stabilized and treated without delay.

There is no guaranteed way to prevent uterine torsion in mares. In many cases, it appears to happen unpredictably during an otherwise normal pregnancy. That means prevention is less about eliminating risk and more about catching trouble early.

The most practical step is close observation of pregnant mares, especially in the last trimester. Contact your vet promptly for any colic signs, repeated discomfort, unusual restlessness, reduced appetite, or behavior that seems different from the mare's normal late-pregnancy pattern. Mild, recurring pain should not be brushed off as routine pregnancy discomfort.

Regular prenatal veterinary care also matters. Your vet can help monitor the mare's pregnancy, discuss when referral is appropriate, and create an emergency plan before foaling season gets busy. If your mare has a history of reproductive complications or you live far from an equine hospital, planning transportation and after-hours contact details in advance can save valuable time.