Late-term pregnancy losses in mares can be sudden, unexpected, and financially and emotionally devastating. The causes range from placentitis (inflammation of the placenta) to viruses such as equine arteritis to noninfectious conditions such as umbilical cord torsions. Placentitis, however, is the leading cause, to blame for around 30% of cases.

Because it can be so difficult to predict pregnancy loss, researchers have been studying various diagnostic biomarkers in hopes of learning more. Barry Ball, DVM, PhD, of the University of Kentucky’s Gluck Equine Research Center, in Lexington, reviewed current as well as newer methods of evaluating late-term pregnancy during the 2016 Theriogenology Conference, held July 27-30 in Asheville, North Carolina. These included:

Estrogens “The equine fetoplacental unit produces (the steroid hormones) pregnanes, androgens, and estrogens during pregnancy, which can be detected in maternal circulation,” said Ball.

A number of studies have evaluated estrogen levels in the blood of pregnant mares. In a 2013 study, for instance, Ball and colleagues studied estradiol (the estrogen sex hormone) levels in pregnant mares and found that they declined in mares with pathology (disease). “Estradiol might have utility evaluating pregnancy status,” he theorized