High Risk Pregnancy in Mares
Dr. Mary Rose Paradis
There is often a large investment, financial and emotional, involved in the breeding and pregnancy maintenance of a mare. Studies have shown that between 25 and 40 percent of mares that are bred fail to produce a live foal. Many reasons exist for this failure to produce healthy offspring. Some of the reasons include:
The causes of abortion, stillbirth and perinatal death in horses are many. In a study conducted in Kentucky by Giles and coworkers, 3,527 cases were investigated. The most common cause of loss of the foal was placental infection caused by bacteria, equine herpes virus, fungi or unknown organism. The second most common cause of death was due to complications at birth, such as neonatal asphyxia, dystocia (difficulty delivering) or trauma. Premature separation of the placenta, twinning, and congenital anomalies were also common.
In some cases, mares with these potential problems can be identified during pregnancy on the basis of their history. They are referred to as high risk mares and are at high risk for serious problems that may compromise their chance for survival during the critical period, from around 300 days gestation onward. Though all mare/foal units should receive the best care and management, pregnant mares at higher risk should be identified. Because a mare or foal is considered at risk, it does not mean that they will definitely get sick and require intensive care. Many do not. However, it is important to have a heightened sense of awareness about the high risk mare's well being, and in some cases, precautionary actions are recommended.
Mares that are experiencing a problem with the current pregnancy or who have had abnormal pregnancies in the past are potential high-risk candidates. For example, twins, illness, weight loss, surgery, anesthesia, and any other major stress during the current pregnancy contribute to risk. In past pregnancies, dystocia, twins, delivery of sick, premature or unusual foals, retained placenta, agalactia (lack of milk production), grazing on tall fescue, infections, untimely vaginal discharge or lactation, or frank illness in the mare during or after pregnancy, put the mare in the high-risk category.
Besides the historical information that is important in identifying the high-risk mare, certain clinical signs are indicative of problems during the current pregnancy. These would include the following:
Premature udder development
If any of the above signs are observed, the mare requires special consideration. The special consideration that the mare should receive depends on your veterinarian's physical examination and diagnosis. Specific treatment is dependent on a specific diagnosis. Certain diagnostic procedures are helpful in determining more specifically what the problem is, and predicting their contribution to potential problems during delivery or after.
When monitoring pregnancy in the high risk mare, each mare is should be treated as an individual. The minimum level of care for the high-risk mare is the close monitoring of the mare until parturition occurs and an attended birth. Placental infections should be treated with appropriate antibiotic therapy. Monitoring usually includes:
Palpation per rectum
A vaginal speculum examination
Transabdominal ultrasound examination
Fetal heart rate determination
Mammary (udder) development
If you have a high risk mare, the first thing to do is to make your veterinarian aware of the problem if he doesn't already know. Second, you should plan on monitoring the mare closely, at least three times a day. You should look for signs of udder development or premature lactation, evidence of impending parturition (loosening of ligaments around the tail, elongation of vulva), vaginal discharge, restlessness, or strange behavior. Sometimes you can observe sweating or signs of colic.
At the time of foaling, an experienced person should be available. If an experienced person is not available, you should consider moving the mare to a facility. You should also prepare a foaling kit that includes a tail wrap for the mare, a bucket for water and disinfectant for washing the mare, dry towels to wipe the foal, scissors to open the placenta if it does not break and 2 percent iodine or chlorohexadine to dip the umbilicus of the foal at birth.