Horse Care – Close Watch

Managing high-risk pregnancies can be challenging but also rewarding

story by Hope Ellis-Ashburn

While managing a mare with a high-risk pregnancy can be a harrowing experience, these pregnancies—with careful management—can and often do result in healthy foals. By becoming knowledgeable about which mares should be considered high-risk, foaling differences for the high-risk mare, and potential ways that you can tip the scales in your favor, you can work as a team with your veterinarian to protect your mare’s health and that of her foal.

What constitutes high risk

According to Julie Strachota, DVM, MS, DACT, director of clinical education and assistant professor of health programs for large animal clinical sciences at Michigan State University’s College of Veterinary Medicine, mares can be considered high-risk for a variety of conditions associated with pregnancy.

“They may have a history of fetal loss or delivering a compromised neonate,” she explained. She also listed a few examples of a compromised neonate, including premature or dysmature foals, septic foals, or foals with neonatal maladjustment syndrome, also known as “dummy” foals. “Mares that have a history of problems in the periparturient period, such as dystocia or difficult birth, premature placental separation, or uterine artery hemorrhage, are also considered high-risk mares.”

Dr. Strachota gave other examples of conditions that would classify a mare as high-risk, including placentitis, twin pregnancies, hydropsical conditions—also known as overaccumulation of placental fluid—ruptured prepubic tendons, and systemic disease. Beyond these, she elaborated that mares can further be considered high-risk based on their reproductive history. Clinical signs that can vault a mare into the high-risk pregnancy category include:

• premature mammary gland development which, Dr. Strachota said, is the most common clinical sign presented to her at the clinic;
• discharge from the vulva;
• unusually large abdomen; and
• acutely painful and colicky mares.

Fortunately, despite the potential pitfalls, Dr. Strachota explained that it is relatively uncommon for a mare to lose a pregnancy after she is at about 100 days of gestation.

“About 5 percent of mares fail to produce a live foal after 100 days of gestation,” she said.

Of those that do, placentitis, which typically occurs from bacteria traveling through the cervix of the mare, compromising the fetal placental unit, is one of the most common causes of fetal loss and abortion during pregnancy.

“Unrelated to pregnancy, a mare may become systemically ill, such as having colic or a fever which results in abortion,” Dr. Strachota added.

Foaling concerns

Regardless of how mares land in the high-risk category, they will be treated similarly, at least in some ways, during labor and delivery.

“It is recommended that mares identified as being high-risk have an observed foaling, which means that someone is watching the mare and spending the night in the barn during parturition,” Dr. Strachota said.

High-risk mare pregnancies are more likely to result in emergencies, such as dystocia or a “red bag” delivery.

“This is because these mares with placentitis are more likely to have premature separation of the placenta, which creates a hypoxic or low blood oxygen environment for the fetus.”

Dr. Strachota elaborated that this is a true emergency and likely one that broodmare owners will have to be prepared to negotiate on their own since a veterinarian may not be able to get to their farm quickly enough to provide aid. That said, while it may be tempting to intervene during the foaling process of your high-risk mare, as long as the foal’s presentation is normal and the foaling itself is advancing normally, it is always advised to leave the mare alone unless she actually does need assistance.

Beyond an observed foaling, Dr. Strachota said that assessment of the placenta after parturition can give a gross indication if the mare had placentitis or placental insufficiency.

“If possible, always assess and save the placenta for your regular veterinarian to assess at the first neonate exam,” she advised. Depending on your veterinarian’s assessment of the placenta, they may recommend further diagnostics and treatments of the neonate.

Foaling at home versus a clinic or hospital

While some mares with high-risk pregnancies may be better off foaling out at a veterinary clinic or hospital, others can be successfully managed at home. Should a mare owner begin to observe signs during the pregnancy that would categorize a mare as being high-risk, Dr. Strachota advises contacting your regular veterinarian first to discuss your concerns.

“Any high-risk mare should be visualized daily by the owner or caregiver to look for any changes, such as premature mammary gland development, vulvar discharge, and relaxation of the pelvic ligaments,” Dr. Strachota said. “These are all signs that something may be abnormal with her pregnancy, especially if she is not to term.”

Then, based on the history, your observations, and a physical exam, the veterinarian would then decide the next steps to take, which could include a referral to a hospital or clinic with your mare’s foaling supervised by veterinary staff, or, a step above even this level of supervision, a high-risk pregnancy program now offered at some major university veterinary hospitals. On the opposite end of the spectrum, if you and your veterinarian decide that your mare can be foaled out at home, work together to decide what foaling supplies you’ll need beyond the normal so that you are as prepared as possible for any potential situations.

Possible prevention

Given the excessive levels of stress and the time devoted to successfully managing the high-risk pregnancy, investigating the prevention of such a pregnancy, if possible, is warranted. Indeed, some of these types of pregnancies can be prevented.

“Placentitis [a condition that interferes with the foal’s blood supply] is one of the most common causes of a high-risk pregnancy,” Dr. Strachota said. “Mares that have poor vulvar conformation are at a greater risk of developing placentitis.”

Dr. Strachota explained that one procedure to reduce the risk of developing placentitis in such a mare is having your veterinarian perform a Caslick’s vulvoplasty. The procedure reinstates the vulva’s function, better allowing it to protect against environmental contaminants.

“This procedure is non-invasive and can be performed on the farm,” she said.

However, mare owners need to consider more than just the mare’s reproductive health prior to deciding to breed her. If the mare has a systemic disease, such as laminitis or pituitary pars intermedia dysfunction (PPID), it is very important that the condition is controlled and managed appropriately throughout the pregnancy.

“While it is a difficult decision, owners need to discuss with their regular veterinarian if it is even a good idea to try to breed such a mare,” Dr. Strachota said.

Reviewing biosecurity practices on your farm is another critical part of protecting your pregnant mare from disease and subsequent risk of abortion. For example, pregnant mares should be separated on the farm from any other horses traveling on and off the farm. Dr. Strachota notes “any horse with a fever, nasal discharge, diarrhea, etc., should be quarantined from the other horses on the farm, especially pregnant mares.”

In addition to isolating sick horses on the farm, other biosecurity practices on the farm also need to be evaluated. Fomites, such as feed buckets, manure picks, grooming supplies, trailers, etc., can all indirectly spread contagious diseases, such as EHV-1. It is recommended that mare owners work with their regular veterinarians to review or even develop biosecurity plans if they are not already in place.

Good, basic mare care can go a long way toward the prevention of misfortune, regardless of the assessed level of risk assigned to any pregnancy. In the article “Expectant Mare: Assuring the Health and Well-Being of the Pregnant Mare,” the American Association of Equine Practitioners (AAEP) recommends that the pregnant mare receive her pre-foaling vaccinations four to six weeks prior to her expected foaling date. These vaccinations include the recommended core vaccinations of Eastern and Western encephalomyelitis, West Nile, influenza, and tetanus vaccines, as well as any risk-based vaccines recommended by your regular veterinarian. They further recommend vaccinating mares against equine rhinopneumonitis (EHV-1) at five, seven and nine months of pregnancy.

In addition to vaccination guidelines, the AAEP advises consulting with your veterinarian to determine the appropriate deworming protocol individualized to your mare’s needs. Observing these protocols along with consistent visits by your veterinarian throughout the pregnancy can work in your favor to ensure that all goes according to plan.

While high-risk pregnancies can be stressful, with safety for the mare and foal as a top concern, an eye toward prevention, knowledge of what constitutes the term “high-risk,” and preparing for potential pitfalls at foaling, even these mares can successfully deliver foals with bright futures ahead of them. HB

Hope Ellis-Ashburn is a freelance writer living in Tennessee. To comment on this story, email us at readerforum@ustrotting.com.