Late Pregnancy Loss in Mares

About 14% of late-pregnant mares in Australia deliver a dead or extremely ill foal that survives only with intensive veterinary care. Bacterial placentitis is the cause of these problems in about half the cases. Early diagnosis and prompt treatment of infection are necessary if foal loss is to be avoided. A recent study supported by Australia’s Rural Industries Research and Development Corporation looked at clinical signs, diagnostic procedures, and treatment of at-risk mares.

Records were examined for mares that had had poor pregnancy outcomes. Ultrasound was the diagnostic method used to determine the severity of the problem, and this factor led to the decision of what treatment to use. Type of treatment proved to be important for the foal’s health and viability. Other things that influenced the foal’s health were the presence of vaginal discharge in the mare and the mare’s having had more than five previous pregnancies.

Transrectal and transabdominal ultrasound examinations can show separation or folding of the placenta as well as fetal heart rate. Evaluation of mares with signs of premature delivery should consider the results of ultrasound examination, detection of vaginal discharge, and a history of previous pregnancies.

In this study, two treatments were used. All mares were treated with antibiotic and anti-inflammatory drugs. Some mares were also given progesterone supplementation. The authors state that more study will be required to identify optimal treatments for mares with signs of premature delivery.