Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock.
Question: Why and when might a veterinarian decide to perform a C-section on a pregnant mare?
Dr. Rolf Embertson, Rood and Riddle Equine Hospital: Most C-sections are performed as an emergency procedure in the horse. The procedure is usually performed when other methods to deliver a foal have failed. C-sections are infrequently performed during colic surgery on a term broodmare and infrequently performed as an elective procedure in the mare. Indications for the latter would include a compromised birth canal due to a previous pelvic fracture or soft tissue trauma, a compromised cervix, previous episodes of postpartum hemorrhage, and previous difficult dystocias.
Dr. Rolf Embertson
Before discussing success rates, a basic understanding of dystocia in the mare is warranted. Dystocia means difficult birth. In the mare, once the chorioallantoic membrane ruptures (the mare breaks water), a foal is usually delivered in about 20 minutes. If a foal is not delivered within about 45 minutes, the probability of foal survival starts to rapidly decrease. Thus, this can become a true emergency where minutes can make the difference in survival of the foal. Although less of an emergency for the mare, her reproductive future and even her life may also be at risk. The goal should be to deliver a live foal in a manner resulting in a live, reproductively sound mare.
There are essentially four procedures used to resolve dystocia in a mare. Assisted vaginal delivery (AVD) is when the mare is awake, possibly sedated, and is assisted in vaginal delivery of an intact foal. This is done primarily on the farm. Controlled vaginal delivery (CVD) is when the mare is anesthetized and the clinician is in complete control of delivering an intact foal vaginally. This is usually done in a hospital environment. Fetotomy is when a dead foal is reduced to more than one part to remove the foal vaginally from an awake or anesthetized mare. This can be done at the farm or in a hospital. C-section is when the foal is removed through an abdominal and uterine incision. This is best performed in a hospital. These procedures are used as needed to produce the most favorable result.
The success rate for live foals and live mares that go through a dystocia is significantly better when the farms are close to a hospital that can perform these procedures. This is primarily due to the duration of the dystocia prior to resolution, although this can be influenced by other factors. Realistic example: A mare breaks water and 15 to 20 minutes later, the foaling attendants realize they can't correct the head back posture of the foal. Within five to 10 minutes (now 20 to 30 minutes since the water broke) the mare is loaded on the trailer, the mare arrives at the hospital in 15 to 40 minutes (now 35 to 70 minutes into the foaling attempt). A brief exam, IV catheter placement, anesthetic induction within five to 10 minutes (now 40 to 80 minutes overall), attempt CVD for five to 15 minutes (now 45 to 95 minutes). If the attempt is not successful, the team will perform C-section, foal is delivered in 15 to 20 minutes from when the decision was made (now 60 to 115 minutes from when water broke).
Dystocia mares that are sent to our hospital go directly to a dedicated induction stall. The mare is anesthetized, her hind limbs hoisted so her pelvis is about three feet off the floor. The foal is examined, repositioned, the mare dropped to the floor, and the foal pulled out of the mare. This CVD procedure is successful in resolving about 75 percent of hospital dystocias. About 25 percent of the hospital dystocias are resolved by C-section.
Following CVD, about 39 percent of those foals survive to discharge from our hospital and about 94 percent of those mares survive to discharge from our hospital. Following C-section about 30 percent of those foals survive to discharge from our hospital and about 85 pecent of the mares survive to discharge from our hospital.
Elective C-sections have a better success rate. There is about a 95 percent survival to discharge rate for foals and about a 95 percent survival to discharge rate for mares.
Dr. Rolf Embertson graduated from Michigan State University with a Bachelor of Science in Zoology in 1976. He also attended Michigan State where he graduated from Veterinary School in 1979 followed by an internship at Illinois Equine Hospital. Dr. Embertson completed a Large Animal Surgery Residency at the University of Florida, followed by an Equine Surgery Residency at The Ohio State University. In 1986, he became a Diplomate of the American College of Veterinary Surgeons. Dr. Embertson is a surgeon and shareholder at Rood & Riddle.
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