Horse-Breeding Issues: Equine Abortion

A twisted umbilical cord can cause problems for your broodmare and unborn foal.

A 14 year-old American Quarter Horse mare presented to the clinic at approximately eight months of gestation with a suspicion of impending abortion. She had been in her outdoor paddock with what appeared to be placental membranes protruding from her vulva. The mare had not shown any signs of labor or abortion. On arrival, the mare was sedated to relieve her anxiety and allow for a safer evaluation.

Initial examination suggested that the tissue visible outside the vulva was an edematous, twisted and hemorrhagic umbilical cord.

Identifying the Problem

In a transabdominal ultrasound examination, no fetal movement or heartbeat was detected. In a vaginal examination, the cervix was wide open. The protruding swollen umbilical cord led to a nonviable fetus. The fetus was within the uterus, lying on its back with its head and front legs flexed. The legs were individually identified and one limb was straightened out at a time. Next, the head and neck were manipulated into an extended position in between the front legs. Gentle traction was applied to extract the fetus from the mare. The umbilical cord was excessively long and severely twisted.

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The fetal membranes were still tightly adhered to the uterus after delivery of the fetus. Consequently, the uterus was lavaged and the mare was administered several small doses of oxytocin during the next several hours. She passed her placenta about six hours after the fetus. Her uterus was lavaged again the next morning, and the mare was discharged. The fetus and placenta were submitted to the Colorado State University Veterinary Diagnostic Laboratory for evaluation. Laboratory tests ruled out potential infection causes of abortion, such as rhinopneumonitis and equine viral arteritis.

About Abortion in Horses

A mare can lose her pregnancy at any stage of gestation without any warning signs. It is always beneficial to an owner or breeding farm manager to determine the cause of abortion in a mare. In some instances, the abortion might be caused by an infectious disease that can be transmitted to other pregnant broodmares, resulting in abortion of multiple mares or an “abortion storm.” From a management perspective, if a mare aborts, she should immediately be separated from other pregnant mares. The reason this particular mare was not in active labor or straining during the abortion process was the location of the fetus. In this instance, the deceased fetus was entirely contained within the uterus and had not yet entered the birth canal. In the normal sequence of events of foaling, major uterine contractions are stimulated once the legs or head enter the birth canal. If fetal membranes had not been visible at the vulva, the issue might not have been recognized as quickly. Twisting of the fetus is a recognized cause of fetal death and subsequent abortion in mares. The length of a normal umbilical cord is 55 centimeters in light-horse mares. An umbilical cord longer than 80 centimeters can be associated with excessive twisting as the mid-gestation fetus moves within the pregnant uterus. Twisting can reduce blood flow within the umbilical cord. A disruption of oxygen and nutrient supply can compromise the health of the fetus. The umbilical cord of this clinical case was 160 centimeters, and it was twisted throughout its length.

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Unfortunately, umbilical cord length cannot be accurately measured in a pregnant mare. In addition, even if the cord length were known, there is nothing that can or should be done to prevent fetal movement within the uterus. Fortunately, umbilical cord problems are not likely to occur again in a given mare and are not known to be inherited.

Member Benefit

It’s practically foaling season, and we look forward to helping you register your new foals! AQHA members get discounted prices on registration. Be sure to register by your foal’s 7-month birthday for the lowest fee. Register your foals online or fax in your form. AQHA Customer Service is here to help with any questions: 806-376-4811.