Equine Dystocia Advancements
Photo: Anne M. Eberhardt/The Horse
Never is timing more important than during a dystocia; managing a difficult birth is truly a matter of life or death. But better understanding of dystocias and the urgency for veterinary intervention means more mares and foals are surviving than ever before.
"Dystocia is any abnormal foaling," says Karen Wolfsdorf, DVM, Dipl. ACT, of the McGee Fertility Center at Hagyard Equine Medical Institute in Lexington, Ky. "Normal foals come out in a specific presentation, position, and posture. Anything that varies from this is called a dystocia. It may be simple, it may be complicated, but it is always a medical emergency."
Stages of Delivery
A normal delivery progresses in three stages. When labor starts, the foal is upside down in the womb, and he has to turn 180Ëš and his legs and head must move into position to slide through the birth canal. So, the purpose of the first stage, which lasts between 30 minutes and six hours, is to position the foal. During this process the mare starts to go off feed. She gets restless and begins pawing, and she paces the stall or the paddock. The contractions have begun. Most times the mare will lie down and roll to help the foal move into position to be born. The signs of the first stage can vary from discomfort that might resemble colic (usually in younger mares) to mild, even undetectable behavioral changes (often in older mares).
The second stage is the actual delivery. The placental membranes, which nourished the foal, rupture and a flood of allantoic fluid rushes out, which is often called breaking water. Once the mare's water breaks, she usually delivers the foal quickly, within 30 minutes.
A foal coming out of the mare's birth canal during a normal birth looks like a diver. He faces the back of the mare, and his head is down by his front legs, which are stretched forward and straight. Two little hooves appear first at the mare's vulva, followed by his nose.
Stage 3 occurs after delivery of the foal. The mare continues to have contractions so she can expel the placenta. If the placenta remains in the womb for more than three hours, it can cause inflammation of the uterus (metritis) and compromise the mare's health.
Wolfsdorf estimates that 1-5% of births in light horse breeds encounter some type of problem during foaling. Miniature and draft horses experience the most problems.
"You want to see a progression in the delivery of the foal," explains Wolfsdorf. "If the mare continues to strain, she gets up, she gets down, you don't see both (of the foal's) feet or she hasn't broken water--these are all signs of problems. You need to see that the foal's feet come, the mare pushes, and the head appears, and as she continues to push more body appears."
When to Call the Veterinarian
If the mare does not deliver the foal within about 30 minutes of the water breaking, or if the delivery does not progress as Wolfsdorf describes, call the veterinarian immediately.
More mares are surviving dystocias than ever before primarily because people no longer wait to call the veterinarian, Wolfsdorf says, and veterinarians don't hesitate to get the mare to a referral center.
Veterinarians generally can correct simple cases of dystocia on the farm if the mare has not been in labor for long. However, if the dystocia is not easily corrected, the veterinarian will need to recover the mare (if she was anesthetized) and refer her to a referral facility, where she can be transported for help, according to Margo Macpherson, DVM, MS, Dipl. ACT, associate professor and service chief of theriogenology at the University of Florida College of Veterinary Medicine. "All of this takes time, which can cost the health of both the mare and the foal," she adds.
More difficult dystocia cases require that the veterinarian create adequate room in the mare to move the foal's head or leg(s) into position for birth. The best way to create room in the mare's pelvis for foal repositioning is to anesthetize her and hoist up her hind end. Hoisting the hind end moves the foal forward in the mare, allowing the veterinarian to manipulate the legs and/or head. However, on a farm hoisting a mare is a difficult process.
"We generally recommend that a veterinarian attempt to correct the dystocia in a standing mare (on the farm) for no longer than 20 minutes, especially with a live foal," Macpherson says. "If the veterinarian is not making progress by that time, it is usually best to send the mare to a hospital where she can be anesthetized and hoisted."
There are four techniques veterinarians use to deliver a foal during a dystocia.
- An assisted vaginal delivery is the most common. The mare is conscious, and the veterinarian provides manual assistance in the delivery.
- A controlled vaginal delivery is performed if the mare must be put under general anesthesia. The anesthesia inhibits contractions, and the veterinarian assists with the ¬delivery.
- A Cesarean section (or C-section) might be performed if a mare's contractions are not strong enough to push out the foal or if there is some other medical reason the mare cannot deliver vaginally. C-sections are most often performed in cases where the mare has a narrow birth canal or when the foal cannot be extracted vaginally due to a deformity or breech position, in which e foal's hips present first. In general, a C-section is the last resort. However, most horses that have C-sections can deliver vaginally next time around.
- ïÂÂ® If the foal is already dead and the mare is not at an equine hospital where a C-section could be performed to extract the fetus, an experienced obstetric veterinarian might perform a fetotomy; he or she cuts the fetus into sections inside the mare and then removes them.
There are many reasons why a dystocia might occur, but the greatest chance for a positive outcome, says Wolfsdorf, is to recognize a problem quickly and seek immediate medical attention for the mare.
In 2007 veterinarians at the University of Pennsylvania's New Bolton Center published a paper that showed the faster a dystocia was resolved, the better the outcome for the mare and the foal. As a result, they developed a coordinated team approach to dystocia management. The "dystocia team" consists of members of the neonatal intensive care unit, obstetricians, surgeons, and anesthetists, together with personnel such as nurses, residents, students, and laboratory technicians. Upon notification of an incoming case, each person is designated a specific task to expedite the process, such as gathering equipment, record and time keeping, preparing the mare for assessment and/or surgery, and monitoring the mare and foal.
In the study, the saved time did not necessarily increase foal survival, but 87% of mares were discharged--an increase from previous figures. If delivery began on the farm and the mare was transferred to the hospital, foal survival was around 20%, but it was 79% if cases known to be high-risk were already at the hospital when the delivery began.
"The survival rates for the foals will always be lower than the mares'," says Macpherson, "because there is a finite period to deliver that foal (as mentioned before, approximately 30 minutes)."
Once the water breaks and labor begins, the foal is deprived of oxygen every time the uterus contracts, which is why he can die so quickly.
At last year's ACVIM Forum veterinary meeting, Katherine Cole MacGillivray, VMD, Dipl. ACVIM, also of Haygard, reported a study similar to the New Bolton one. Over a two-year period Haygard handled 172 dystocia cases; 121 live foals were born and, of those, 88 were discharged from the hospital. "Our overall survival rate is about 50%," MacGillivray said at the meeting. In the past only 10-29% of foals survived a dystocia, she added. She speculates that the improved survival rate results from mares and foals receiving more immediate emergency care than in the past.
The foals that survived birth exhibited severe problems such as neonatal encephalopathy (dummy foals), sepsis (blood infection), and rib fractures, and about 50% of the foals required resuscitation after delivery and received assisted ventilation and/or injectable medications.
But it's important to note that because veterinary staff and equipment were readily available, half the dystocia foals survived, and "if you are born alive, (and without signs of an infection) you have a 70% chance of making it," she said.
Dystocias In Real Life: Down on the Farm
When the veterinarian arrives to assist with a dystocia, he or she will examine the mare to determine the foal's position. Fortunately, the most common cause of dystocia is also one that can usually be "fixed" on the farm."The outcome depends on the severity of the dystocia," says Wolfsdorf. "If you only see one foot coming out, you can reach in there and, if the other foot is just bent, you can correct the foot and the mare goes ahead and delivers. That is your best-case scenario."
Another common reason for dystocia is a little more serious--the foal's head is in the wrong position. In this case the veterinarian might be able to push the foal back into the womb, reposition the head, and the mare can deliver the foal normally. However, shortage of natural lubrication is a concern with most dystocias; a veterinarian should provide liberal amounts of obstetrical lubricant before trying to manipulate the foal inside the mare. This not only assists the foal through the birth canal but also helps prevent damage to the mare's delicate reproductive tract.
Even though a dystocia requires an experienced hand, owners and farm managers can do a few things to help the veterinarian:
- If the birth does not progress as described earlier, call the veterinarian right away. That is the single best way to help the mare and the foal.
- While you are waiting, prepare the mare so the veterinarian doesn't have to take time for this. Wrap the tail and wash the perineal area, which includes the anal area, vulva, and tissues between, with warm water and mild soap.
- Try to keep the mare calm and standing or walking as you might do for a colic case. "When a mare is in distress, she will strain and push, because she wants to push that baby out even though it can't come out," says Wolfsdorf. "That intense abdominal pressure can prolapse their rectum, rupture the uterine artery, or rupture part of the bowel," all of which could have dire consequences. Walking her around might stop her from pushing so hard.
- Hook up the trailer, and be prepared to move the mare to a referral center if she can't be helped on the farm.
After the Fact
Following a dystocia, most mares can be bred again, Macpherson says, although they can still have problems such as retained placenta, metritis, uterine trauma or tears, trauma and tears of the caudal portion (back, toward the tail) of the reproductive tract, bruising or rupture of the intestinal tract, and peritonitis (inflammation of the abdominal lining), that require medical and possibly surgical attention. Therefore, how soon a mare can be bred back might depend on how early in the breeding season the dystocia occurred, how serious the dystocia was, and whether the mare required any surgical repairs, according to Wolfsdorf.
"Every mare that has a dystocia needs a full breeding examination well after she has healed from the event to see where she stands as far as future breeding," adds Macpherson.
Just because one pregnancy resulted in dystocia doesn't mean subsequent ones will, although if a mare has a condition (such as laminitis, poor vulvar conformaion, a history of abortion, or old age, among others) that does put her in a high-risk category, veterinarians might suggest she be taken to a referral center prior to her next delivery.
"Dystocia is a rare occurrence," says Macpherson. "The beauty of working with horses is that mares deliver their foals very efficiently and very well. But while they are rare occurrences, it is a time-sensitive emergency, and the faster you address it, the better your chances of saving the mare and the foal."
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POLL: University Equine Hospitals