Dystocia in Mares

Whether it’s your first foal or your hundredth, you always feel a great sense of anticipation waiting for your mare to give birth. You have hopes and expectations for that baby and future plans for the mare. Fortunately, in most cases, the mare gives birth to a healthy foal. But in some situations the foal doesn’t arrive as expected or scheduled, resulting in dystocia, or a difficult birth. When that happens, every minute counts if you’re going to save both mare and foal.

Causes and Types of Dystocia

Maria Schnobrich, VMD, Dipl. ACT, a theriogenologist and shareholder at Rood & Riddle Equine Hospital in Lexington, Kentucky, defines dystocia as a difficult birth in which the mare does not deliver the foal within the typical 30-minute time period or in a normal presentation, position, and posture. In Stage 1 of labor, the foal rotates from being positioned on his back to extend his front feet and head into the birth canal. In Stage 2, from the time the water breaks until delivery, the foal is born with the front feet first, followed by the head resting on top of the front legs. Anything that interferes with this normal delivery process can result in dystocia.

In the mare, causes can include uterine inertia (failure of the uterus to contract correctly, giving the foal inertia to pass through the birth canal), body wall tears, uterine tears, or systemic disease. Problems such as fescue toxicity (from grazing endophyte-infected tall fescue in late gestation) and electrolyte imbalances that alter the uterus’ or placenta’s normal function can put mares at increased risk of dystocia. In addition, if the mare is frightened or stressed, she might position herself in a way that prevents the foal from aligning correctly for delivery. Finally, problems can arise if the cervix fails to relax, tissues prolapse, or the foal’s feet get caught at the top of the birth canal.

The foal can also be positioned in a way that doesn’t allow him to exit the birth canal normally. He could be facing the wrong direction or have a fetal deformity that prevents normal positioning, or he could be one of a twin trying to come out at the same time.

Patricia Sertich, MS, VMD, Dipl. ACT, associate professor-clinician educator at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, in Kennett Square, says that incorrect fetal posture and positioning is by far the most common cause of dystocia in the horse.

The fetus rarely grows larger than the mare’s pelvis, so its size is typically not the issue. It is the foal’s long legs and neck that, improperly placed, can prevent passage through the birth canal. Congenital (present at birth) or fetal abnormalities are rare but can happen.

Dystocia in Mares

Schnobrich and Sertich both stress the importance of recognizing another cause of dystocia—a red bag delivery. Throughout most of pregnancy, the foal is surrounded by the amnion (placental membrane) and amniotic fluid. The outermost layer of tissue surrounding the amnion and fetus is the chorioallantois, which comes in direct contact with the uterus. In a red bag delivery the chorioallantois doesn’t rupture, and the fetus can be expelled encased in all the membranes. When this happens the foal loses its placental blood and oxygen supply and can die. Instead of first seeing the fetus surrounded by a white membrane as it passes through the birth canal, you see a velvety mass at the mare’s vulvar lips.

“If a foaling attendant sees a red ball at the vulva, they need to know that is an absolute emergency,” says Sertich. “They need to manually rupture the red membrane and assist in getting that foal delivered by providing manual traction.”

Potential Risks to Mare and Foal

The most serious risk to both mare and foal in the event of a dystocia is death. Plain and simple, if the foal doesn’t come out, the mare will die. For the foal, a delay in delivery can result in hypoxia, or a lack of oxygen, that could cause lifelong abnormalities, or it can incur trauma associated with delivery process.

Mares can die from uterine rupture, rupture of a major blood vessel, or prolapse of the bladder or intestine. Retaining the placenta can lead to life-threatening systemic illness and laminitis. Non-life-threatening issues include vaginal lacerations, cervical tears, trauma to the pelvic canal that can result in urinary incontinence, and neurologic deficits. Mares can also experience future fertility issues depending on the severity of the dystocia.

Prepare in Advance

Sertich recommends learning everything you can about a normal delivery so you have a better chance of catching anything abnormal, and Schnobrich suggests closely observing mares in late gestation. Typical gestation length ranges from 321 to 365 days. Within the month leading up to foaling, mammary development occurs, and the teats fill with milk two days to one week prior to foaling. At this point it’s important to provide round-the-clock observation. You can monitor sodium, potassium, calcium, and pH levels in the mammary secretions, which usually begin 48 hours before parturition (birth). However, mares with abnormal pregnancies that have been dripping milk might not show these changes.

Like many situations, a little preparation will go a long way in the unlikely scenario that something is wrong. Both Sertich and Schnobrich stress making decisions long before the mare foals.

While most breeders know a mare’s due date, Sertich emphasizes the importance of the veterinarian knowing her breeding and/or ovulation date, as well.

Talk with your veterinarian early in the pregnancy about what to do if a problem arises. Determine which mobile vet you’ll call or hospital you’ll take the mare to should a dystocia occur. Have a truck and trailer ready so you can transport the mare quickly if necessary. If you’re caring for someone else’s broodmare, plan important care decisions with the owner ahead of time in case he or she is not present when the mare goes into labor, or make sure you can reach the owner if things go awry.

Then discuss answers to a number of questions so everyone—your barn personnel and veterinarian—knows the priorities. It’s a difficult question, but ask yourself which animal is more important if you can only save one—the mare or the foal? Is the dam a commercial broodmare or your favorite companion? Do you want to breed her again? How much is the foal worth financially and emotionally? Can you pay for a cesarean section or hospital care? These fees can easily run into the thousands of dollars.

Understanding the Delivery Process

“It is incredibly important to know the timing of delivery,” says Schnobrich. “Know when the water breaks, and make note of the time because the foal should be out within 30 minutes. If it’s longer than that and things are not progressing, something is wrong. The mare needs to be examined or sent to the hospital.”

How long have you noted mammary development, and how long has milk been dripping? “The more everyone (on the veterinary team) knows, the better job everyone can do and the better the outcome.” Sertich says.

Fetal fluids passed with the placenta should be yellow, colorless, or clear, and you shouldn’t see many red blood clots. The mare’s heart rate shouldn’t be continuously over 75. If it is, she might be experiencing a disruption in her cardiovascular system or excessive pain. And, while mares commonly push and then rest, stopping for any length of time could indicate a problem.

With a normal presentation, you’ll see the foal’s front feet first, followed by his nose on top of the legs. If 20 to 30 minutes pass and you haven’t seen this, call your veterinarian. If you can see feet, try to figure out if they are front or back legs.

“Front legs have fetlocks and carpi (knees) that will flex in the same direction,” says Schnobrich. “Fetlocks and hocks bend in the opposite direction.”

If the mare hasn’t yet delivered the foal and the veterinarian is on the way, you can take important steps in the interim. Schnobrich suggests getting the mare on her feet and walking her to prevent her from actively straining until the vet arrives. If the foal’s front legs and head are out, you can breathe into its nostrils to inflate the lungs (make sure the nose is cleared, hold off the down nostril with one hand while breathing into the up nostril, and deliver no more than 10 to 20 breaths per minute).

Upon arrival the veterinarian will quickly but comprehensively examine the mare to see if she is stressed or dehydrated. He or she will perform a vaginal exam and make a diagnosis. If the mare is severely stressed, she might need to be sedated. Once the examination is complete, the veterinarian will determine whether the mare can safely deliver at the farm or if she should be transported to a hospital.

Some practitioners can correct dystocias in the field, but time is of the essence. Breech and dog sitting positions are two presentations that are almost impossible to fix at the farm but, ultimately, it is up to the veterinarian to determine what corrections he or she can make.

If you decide to keep the mare at the farm, the veterinarian might administer sedation to the standing mare or general anesthesia to lay the mare down and raise her hind legs. The latter moves the intestines forward and allows for much more efficient correction of the dystocia. The veterinarian might provide mild traction, or manual pulling, to aid in delivery, but if the fetus still isn’t emerging, he or she will need to reassess the situation. The mare might need more lubrication or a change in positioning.

If possible, both Sertich and Schnobrich advise sending the mare to the hospital in a timely fashion to give both mare and foal a better chance of survival.

At the Hospital

Many referral hospitals have a dystocia team on call. It consists of a reproductive specialist, anesthesiologist, surgeon, neonatologist, and nursing staff. When the call comes that a dystocia is on its way, the team mobilizes.

“This is one of the greatest things we do at New Bolton,” says Sertich. “Everyone knows their jobs and gets to work right away. It’s like a symphony. The reproductive vet has 15 minutes to get the foal out of a standing mare. If not, general anesthesia is administered, a controlled vaginal delivery is attempted, and if needed a C-section is performed. The goal is to have the foal out within 20 minutes of the mare arriving.”

Unfortunately, if the mare goes downhill, so does the fetus. If the mare cannot be saved, the veterinarian may perform a terminal C-section.

If the foal is delivered successfully and the mare survives, the veterinarian needs to evaluate her over the following days. This includes monitoring her temperature to catch problems early. Schnobrich says post-foaling complications include retained fetal membranes, metritis (uterine inflammation), significant reproductive tract trauma, and cervical tears. It is also important to manage the mare’s pain and anxiety so she produces adequate milk.

Saving the Foal

If the mare doesn’t make it, the foal needs immediate attention. After three hours the foal should be standing and nursing, and it absolutely needs colostrum (the mare’s antibody-rich first milk). It is possible to milk colostrum from the deceased mare, but it must be negative for antibodies that cause neonatal isoerythrolysis (a condition that destroys the newborn foal’s red blood cells; this can happen if there is abnormal blood transfer between the fetus and the mare, such as placental hemorrhage during pregnancy, and she develops antibodies against the foal’s blood type). If colostrum is not readily available, you can use plasma to supplement antibodies.

Then consider how to raise the foal. One option is to get a nurse mare; another is to induce lactation in a barren mare. If another mare is not available, the foal can be hand-raised. Fortunately, you can purchase high-quality milk replacers or feed preformulated mare’s or goat’s milk. Talk to your veterinarian regarding amount and frequency. Finally, it’s important to have orphan foals socially interact with other horses so they learn horse manners.

What’s New?

Schnobrich is a proponent of having the veterinarian perform at least one late gestational transrectal ultrasound and, if possible, a transabdominal scan on the mare around 300 days. This often helps the veterinarian catch abnormal thickening of the placenta, changes in fetal fluids that indicate fetal stress, and, occasionally, fetal abnormalities. This information can help you better prepare for a possible issue.

Transabdominal ultrasound technology continues to advance. It makes things easier to see but, even if everything looks correct, you have no way to know for sure that a dystocia will not arise.

One current area of study, says Sertich, is how to determine when a fetus is mature enough for delivery. Veterinarians measure electrolyte concentrations in mammary gland secretions to determine this in normal mares. More recently researchers have looked at the motility of the fetal gastrointestinal track using ultrasound as an indication of maturity or readiness for foaling. Scientists are also testing new equipment used to monitor uterine contractions in dogs on horses so they know parturition is imminent.

Take-Home Message

Most mares deliver normally and present their owners with healthy foals. But before that can happen, it is vitally important to be prepared, discuss options, and make decisions with your veterinarian so you can implement an emergency plan rapidly. This will increase your chances of ensuring the health and welfare of both mare and foal if a dystocia occurs.