Perinatology: End of Pregnancy Through Beginning of Life
Traditionally, one of the stronger parts of each AAEP convention program is the time devoted to reproduction. The convention held in Orlando was no exception. It began with an in-depth session titled "Perinatology--End of Pregnancy Through Beginning of Life," during which experts in the field presented hour-long lectures on various reproductive problems, and it ended with two separate sessions of 20-minute lectures in which the presenters dealt with specific reproduction topics.
In-depth presenters were Wendy Vaala, VMD, Dipl. ACVIM, who is employed by Intervet Inc.; Margo Macpherson, DVM, MS, Dipl. ACT, of the University of Florida; Regina Turner, VMD, PhD, Dipl. ACT, of the University of Pennsylvania's New Bolton Center, and Robert Franklin, DVM, Dipl. ACVIM, a referral hospital veterinarian based in Ocala, Florida.
Late-Term Mare, Newborn Foal
Leading off in the in-depth section and continuing on as moderator was Vaala. She offered "New Perspectives on the Late-Term Mare and Newborn Foal."
Under ideal conditions, Vaala told the group, the late-term mare would be managed before birth by a specialist in reproduction and after birth by a specialist in neonatology. However, she said, in most ambulatory practices, one person must be prepared to fill both roles, have proper equipment to assist in birth and, if necessary, provide resuscitation and nursing care for the foal.
Many problems begin within the uterus, she told the group, and the practitioner must be able to monitor fetal development in order to determine early if something is going awry.
When a mare, especially one in the at-risk category, nears parturition it is important to monitor her progress so that help is at hand if needed. There are many monitoring aids available, she said, but no one aid should be considered infallible. "Nothing beats a human walking by and checking on the mare," said Vaala.
One of the problems that occur is prolonged gestation. It is important that the practitioner has a complete history of the mare, including whether she has been kept on fescue. There are some 35 million acres of fescue in the United States, Vaala said, and fescue toxicosis from infected varieties can lead to prolonged gestation and myriad other problems that can compromise the foal's chances for survival.
The drug of choice in dealing with fescue toxicosis, she said, is domperidone.
Once the foal has been delivered and the fetal membranes passed (something that should occur within three hours of delivery), Vaala told the group, it is very important that you save and weigh the placenta. The weight of a placenta, which can be 10-11% of fetal weight, can be an indicator that problems might exist with the newborn. Heavy placentas, she said, might be associated with conditions such as edema (fluid swelling), congestion, and/or infections. A light placenta might relate to incomplete development of the foal, along with other conditions.
Inducing labor in a late-term mare, Vaala said, should only be used as a last resort. "Indications for induction should only be limited to conditions that would seriously threaten maternal or fetal health if the pregnancy were allowed to continue, or if unsupervised, spontaneous delivery would occur," she said. "Examples of such conditions include hydrops (excessive placental fluids), prepubic tendon rupture (tearing of the ligament that supports the abdomen in the mare--loss of this structure makes it impossible for mares to contract muscles and deliver the foal normally), imminent death of the mare because of colic or other systemic illness, and maternal history of dystocia requiring mandatory assistance during foaling."
The quality of the mare's colostrum, which Vaala called "liquid gold," should be evaluated immediately after delivery, she said.
Vaala noted in her written paper: "Equine perinatology has evolved rapidly over the last two decades. However, most mares will continue to foal in locations other than in large clinics and university hospitals. Therefore, it will remain in the hands of clinicians in private practice to help improve our knowledge of the high-risk mare by using and reporting on the use of the antepartum (pre-foaling) monitoring techniques and interventional strategy discussed in this presentation."
Macpherson concentrated on "Identification and Management of the High-Risk Pregnant Mare" in her lecture. There are a number of conditions that can jeopardize the pregnant mare, she said, and the practitioner's challenge is to identify those problems, then find proper approaches to resolve them.
Three common conditions, she said, are early udder development, acute pain, or an unusual increase in abdominal size. For each condition, she presented the case history of a mare that had suffered from the condition.
Two of the conditions that can cause early udder development are the presence of twins and bacterial placentitis (inflammation of the placenta), Macpherson told her listeners.
In the case of twins in late gestation, she said, the best approach has already been missed. That would involve early detection at 13 to 15 days gestation and the elimination of one embryo. Carrying twins to term puts the mare at risk for a number of complications, including dystocia (difficult birth), Macpherson said. Once twins reach the late-term stage, she said, there are basically two options left for the practitioner: terminate the pregnancies, or allow the pregnancies to continue, monitor the mare, and provide assistance during delivery. Neither is particularly palatable to the practitioner, she said.
A promising approach for treatment of bacterial placentitis, Macpherson said, involves administering trimethoprim sulfamethoxazol and pentoxifylline in conjunction with altrenogest (Regu-Mate).
In a study at the University of Florida, she said, 10 of 12 mares with experimentally induced placentitis delivered live foals after treatment with this protocol.
The colicky late-pregnancy mare poses a serious challenge for the practitioner, Macpherson said, because it first has to be determined whether the manifestation of pain is from labor contractions or some other condition not connected with the birthing process.
Once the diagnosis had been made, a treatment protocol can begin. It is important to have a complete health history of the mare, Macpherson said. For example, if she has a history of colic when not pregnant, there could be greater likelihood of her having gastrointestinal disease than a type of colic related to pregnancy.
The case study mare Macpherson described underwent colic surgery and four days later delivered a live foal.
A mare in late pregnancy that develops unusual abdominal distention is frequently in great jeopardy, Macpherson said, and she is at risk of losing the pregnancy. There are several conditions that could cause the problem, including hydrops, rupture of the prepubic tendon, and abdominal wall herniation.
Treatment options, she said, could involve use of a supportive belly bandage, induction of labor, and delivery by Caesarean section.
Turner told the group that when she began preparing her presentation, she had decided to discuss her top 10 list of postpartum problems in mares. Then she realized that there wouldn't be enough for that lengthy of a presentation and cut it back to five, then to three.
The three problems she chose were 1) hemorrhage from uterine or ovarian vessels, 2) uterine lacerations, and 3) retained fetal membranes.
Hemorrhage from uterine or ovarian vessels usually occurs during the birthing process, Turner said. Older mares that have had a number of foals appear to be at greater risk.
Treatment of the condition, she said, can be difficult and confusing. The practitioner must decide whether to place the mare in a tranquil setting to lower stress and blood pressure, or whether he or she should institute aggressive treatment that might increase stress and blood pressure.
"In most instances, as a minimum," she said, "we will place an indwelling venous catheter and begin the mare on volume replacement fluid therapy." She discussed some of the drugs that have been used to treat the condition and others that are not recommended.
The prognosis for recovery is variable, depending on the severity of the hemorrhage, she said. "Mild hemorrhage into the broad ligament (a band of tissue the helps suspend the uterus within the abdominal cavity) typically is associated with a good prognosis for recovery," she said. "However, severe hemorrhage into the abdomen or uterus can be acutely fatal."
If the mare survives, she said, a future pregnancy might result in a recurrence. If the mare is a valuable producer, Turner said, embryo transfer should be considered.
Turner then turned her attention to retained fetal membranes. In the mare, she said, it is considered that fetal membranes have been retained if they have not been passed in their entirety in three hours.
The condition can occur in any breed, she said, but it is most common with draft mares. Friesian mares, she said, are at a significantly higher risk, even after an uncomplicated delivery. She described one study where 54% of Friesian mares retained their fetal membranes after normal delivery.
When membranes are retained, Turner said, the treatment of choice by many practitioners involves administering oxytocin. Forceful removal is not a wise approach, she said, but gentle pressure can be helpful, along with uterine lavage.
One of the problems involved with Caesarean section, Turner told the group, is that it often is resorted to only after prolonged attempts for a vaginal delivery. Delivery of a live foal after Caesarean section, she said, results in foal survival rates of 11-42% and survival of the foal from the hospital is lower still at 5-31%.
"The wide range in foal survival consistently depends on duration of second-stage labor," she said. "Thus, whether or not a mare has a Cesarean section is not what determines the outcome for the foal. Rather, it is how long it takes for a foal to be delivered, regardless of delivery method--this is the critical factor."
She had this succinct advice for the practitioners in the room: "Refer early."
Mares that undergo Caesarean section and have good postoperative management often have pregnancy rates that range between 58-68% if bred back that year. If bred back the next year, the rate rises to about 72%.
Franklin closed out the in-depth session with a discussion on "Identification and treatment of the High-Risk Foal."
Early identification of high-risk foals is imperative so that successful treatment can be initiated in a timely manner, he told the group. However, identification is only the beginning of the process. The ambulatory veterinarian should be equipped with appropriate equipment for resuscitation, assisting with breathing, and increasing heart rate.
A valuable tool, Franklin said, is an instrument that measures lactate levels (in the blood). High lactate level can be an indicator that the foal is in the at-risk category.
One of the new approaches described at this AAEP convention involved equipping attendees at some lectures with keypads for responding to specific multiple-choice questions, which then were immediately tallied by computer. The keypad response in one instance provided evidence that very few veterinarians attending the session utilize the lactate-measuring machine. Franklin made a strong pitch for its use and cited a number of examples where the device had first identified at-risk foals, then was helpful in monitoring their recoveries.
A later presentation would underline his point that measuring lactate levels can be helpful at both the diagnostic and monitoring levels.
Franklin said in conclusion: "It is obvious that early recognition of the high-risk or abnormal foal is the key to a successful outcome. Efforts and financial contributions should be made early in the course of the foal's life to document all problems so that an appropriate prognosis and treatment plan can be made. Mares with peripartum disease should be monitored closely for foaling trouble or for the delivery of a compromised foal. Preparations in terms of equipment for resuscitation, veterinary planning, and foaling attendance are critical to the successful delivery of a high-risk foal."
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.