It's nearing the best time of the year again--foaling season. Although most foals are born in the spring of the year, between February and June, sometimes we see foals in late December or early January. Often these tiny newborns delivered to our hospital around Christmas are preemies (premature foals), but of course, premature foals can be delivered at any time during the season. In the past, a premature foal was regarded as a lost cause with little chance of survival and less hope of being an athletic adult. However, prematurity is not a death sentence anymore, nor is it an automatic label of "non-athlete." With the establishment of neonatal intensive care units in many university and private practice equine hospitals, the survival rates are increasing. Our knowledge and understanding of the problems associated with premature foals also are increasing, thus helping us treat these foals more effectively. Premature foals often require intensive care to survive, but with the proper treatment, many of them can and do survive.
So, what do you do if your foal is delivered early? How do you know if your foal is premature? What are the problems to be aware of? Why was the foal delivered prematurely in the first place? In this article, we will define what a premature foal is, describe the complications that occur with premature foals and their treatments, and also describe some of the reasons premature foals are delivered so early.
What Is A Premature Foal?
Many premature foals require intensive care in an equine clinic and are administered intravenous glucose along with intravenous nutrition.
Normal gestation (pregnancy length) in a mare is anywhere from 320 to 365 days, with an average of 341 days. However, normal, healthy foals have been delivered anywhere from 305 to 365 days. Foals born before Day 300 usually are considered nonviable.
A foal is considered premature if delivered before Day 320 of gestation. Unfortunately, each individual mare will have a different gestational length. Knowing the previous gestational length of your mare can help you plan for delivery, as mares often carry subsequent foals for a similar gestational length. This is why knowing her breeding dates is so important--so that you can count back and determine the gestational age of your foal and not have to guess.
Unlike humans, pregnancy length in mares, is not related to fetal maturation. In humans, it can be safe to induce labor if a woman is in the last two weeks or so of pregnancy and the baby will be mature. In horses, the length of pregnancy is so variable that you cannot rely on the length of pregnancy to determine if the foal is mature. This is extremely important for mares which need to have the birth process induced (begun artificially) so that they can be attended, such as mares with pre-pubic tendon ruptures (this is a tearing of the ligament that supports the abdo-men, and loss of this structure makes it impossible for the mares to contract their abdominal muscles and deliver the foal normally) or other problems.
Just because the mare is "full term," meaning her pregnancy has lasted 340 days, does not mean the foal will be fully mature and ready to handle life outside of the uterus. It's a risk.
A premature foal is not just born before the expected due date. He has not been able to complete developing inside his mother's uterus; therefore, certain body systems often are not quite ready for extrauterine life. There are other birth terms to be aware of such as "dysmature" foals. These foals are born within the normal gestational length, but have the physical characteristics of an immature foal. Dysmature foals can result even though the foal underwent a normal gestation--say 330 days. However, it is possible that this particular mare usually has a gestation of 350 days, so the foal might be 20 days early, resulting in an immature foal.
As we have already determined, foals born before 320 days of gestation are by definition premature. However, there are other physical characteristics that define prematurity as well. Premature foals have low birth weights, meaning they often weigh much less than the 90-100 pounds of normal foals carried to term. These foals often are weak at birth, so it might take them longer to stand and nurse than normal foals. (Normal foals should stand and nurse within two hours of birth.) Premature foals often have a short hair coat that feels like silk, with very soft, pliant ears. They also frequently have dropped fetlocks (lax flexor tendons), most common in their hind legs. Premature foals also often look quite thin, due to the low body fat stores.
Foals can be delivered prematurely for a variety of reasons associated with the dam, the placenta, or the foal itself. A foal might be delivered early, for example, if the mare has an accident and suffers a broken leg or has a severe bout of colic that could necessitate the euthanasia of the mare. However, the foal, if past a certain gestational age (usually Day 300), can be delivered early via cesarean section just before the mare is put down. If the foaling must be attended by a veterinarian (for example, if the foal is at risk of neonatal isoerythrolysis), the mare can be induced to deliver her foal prematurely. If the breeding dates are unclear or unknown, then the mare is at risk of delivering a premature foal.
Spontaneous delivery of a premature foal also can occur. One of the most common causes of premature delivery is placentitis (infection within the placenta). The infection within the placenta often crosses to the foal and usually results in abortion or premature delivery. Other causes of a premature birth could be the result of twinning, or congenital problems associated with the placenta or the foal (such as overtwisting or torsion of the umbilical cord causing poor fetal circulation and not allowing the bladder of the fetus to empty properly).
Many of the foal's body systems don't complete full development until the last week of gestation. So, foals born prematurely even by just a week or two often have difficulty adapting to life outside the uterus. This could be seen as simply the inability to maintain body temperature. However, there are many more complex problems associated with prematurity.
Premature foals usually are quite susceptible to infection within the lungs and can have problems with the inability to breathe adequately due to an immature respiratory system. An immature musculoskeletal system predisposes them to angular (crooked legs) and flexural deformities (dropped fetlocks and contracted tendons). An immature endocrine system does not allow them to respond appropriately to stressful situations (disease) as their white blood cell count is often quite low. So, you see, there is a lot more to premature foals than just small size.
Premature foals have been known to have problems maintaining their normal body temperature--known as thermoregulation. Although all newborn foals are susceptible to hypothermia (low body temperature), premature foals are particularly susceptible. Normal rectal temperature in a foal is between 100ï¿½ and 102ï¿½ Farenheit. Foals will help maintain their body temperature by shivering.
Premature foals should be treated with extra caution. They should be dried shortly after delivery and should be kept inside to prevent wetting from rain or snow. They also should be kept warm with blankets and stabled away from drafty areas within the barn. Heat lamps can be placed within the stall to allow for the foal to get warm, but make sure the foal can move away from the heat source if he becomes too warm.
Premature foals have few fat stores, so preemies are very susceptible to hypoglycemia (low blood sugar). These foals, if not able to nurse on their own, must be bottle fed or tube fed by a veterinarian, in order to receive the colostrum they need. Sometimes the foal is delivered and no colostrum or milk is available, so another source of colostrum must be found quickly.
All foals need milk within a few hours of birth, but premature foals are particularly prone to "fading" without glucose from the milk. Another problem associated with premature foals is that their gastrointestinal tract might not be able to handle digesting the milk, so they must be fed intravenously, to prevent bloating and colic. Because of this, many premature foals require intensive care in an equine clinic and are administered intravenous glucose along with intravenous nutrition.
One of the most common body systems affected by prematurity is the musculoskeletal system. The foal's bones [especially those of the carpus (knee) and tarsus (hock)], ligaments, and tendons often are not fully developed. This causes angular and flexural deformities. The flexural deformities usually are in the form of tendon laxity, which usually resolves as the foal grows and becomes stronger. Angular deformities, which result in the foal's legs looking crooked, often are the result of incomplete ossification of the carpal and tarsal bones. Without treatment, the foal's bones within these joints can become crushed, leading to serious angular limb deformities.
Radiographs of the foal's carpal and tarsal bones can tell the veterinarian if the bones are fully developed. If there is incomplete ossification, then treatment with splints or tube casts (casts applied to the legs, but which do not enclose the hooves) is recommended to prevent the "crushing" syndrome and allow for full ossification of these bones without further problems.
Another complication associated with premature foals is the high probability of respiratory problems. This usually is multifactorial, but can occur in the form of lung infection (pneumonia), lung collapse, and just plain immaturity of the lung. Many premature foals require surfactant and oxygen supplementation to overcome these problems and allow normal oxygen levels in the blood.
Oxygen is often delivered through a small tube placed within the nostril. Some foals might need to be placed on a respirator if lung dysfunction is severe. If pneumonia is present, then X rays (radiographs) can reveal the severity of the infection. Treatment involves aggressive antibiotic therapy, if the pneumonia is caused by bacteria.
What's The Prognosis?
Premature foals can survive. Even foals born before Day 300 of gestation have been reported to survive and thrive with aggressive intensive care. However, whether or not a premature foal will survive often depends on several factors.
The first of these factors is why the foal was born premature. Research on premature foals has revealed that foals born as a result of cesarean section or induction of labor have a far lower chance of survival than foals born to mares with chronic uterine infection. This is most likely due to the endogenous steroids released during a foal's "stressful" life within the diseased uterus helping his body systems--especially the lungs--mature. Therefore, when the mare with a uterine infection delivers her foal, it will be premature and it will be septicemic (infection within the bloodstream due to the infection within the uterus), but the body systems, especially the lungs, are more mature than the cesarean section preemie which was delivered with no "stress."
Foals born from mares with infection, if treated within 24 hours of birth, often have a greater than 70% chance of survival. However, foals delivered via cesarean section or those which were artificially induced due to sudden illness or injury of the mare are reported to have only a 10-20% survival rate. So, in the case of premature foals, stress before delivery can be good.
The second factor in the prognosis for a premature foal is the ease of the delivery. If there was a dystocia (difficult birth) or any other cause for decreased supply of oxygen to the foal, such as premature separation of the placenta, then the result could be a more complicated clinical outcome. The decreased oxygen can lead to neonatal maladjustment syndrome, in which a foal displays normal behavior after birth for up to 24 hours, then begins to display abnormal behavior such as lack of or decreased suckle reflex. This leads to decreased or no nursing, lack of interest in the mare, or even seizures.
This syndrome complicates the treatment for an already complicated premature foal.
Another problem seen during delivery occurs when the foal becomes severely stressed during the delivery. The meconium (first manure) might be expelled by the foal while still in the uterus. The foal can aspirate the feces during his attempts to breathe. Aspiration of this meconium can lead to severe pneumonia in the foal. This not only compromises already fragile lungs, but seeds the rest of the body with bacteria, leading to sepsis (infection).
The third factor in assessing the prognosis of a premature foal is the degree of the immaturity. Obviously, the lower the gestational age, the more potential complications associated with immaturity and the higher the difficulty in sustaining the severely immature foal. Foals which are only a week or so premature might require only observation or just minimal treatment to result in a healthy foal, while foals on the other side of 300 days gestation will need around-the-clock intensive care, possibly even artifical respiration.
The fourth factor in the prognosis and in the decision on whether to treat the foal--the financial aspect--is purely up to you. Intensive care for a premature foal is not only time consuming, but complicated, with multiple drug regimens to keep the premature foal's body functioning properly. There must also be a facility with the equipment and staff to care for an equine neonate. The original estimate of seven days of therapy can extend into weeks of treatment at an equine clinic, depending on any number of complications that the foal might encounter. Neonatal intensive care units involve around-the-clock care, veterinarians on staff, technicians, and nurses.
The value of the foal, the condition of the foal at the time of veterinary evaluation, and the ability or inability to pay for the treatment are factors to be considered in making a decision. An owner must realize that a decision to euthanize due to financial concerns does not make him or her a bad person. I have seen many foals lie for weeks in intensive care with many thousands of dollars being spent to save them only to have them succumb in the end to overwhelming infection--it's often a gamble.
What To Do With A Preemie?
Usually, when a mare is going to deliver a premature foal spontaneously, you will see udder development or vulvar discharge and signs of impending parturition a few days to weeks in advance. If any of these signs occur in your mare much earlier than they are expected, you should contact your veterinarian immediately. Your veterinarian will examine the mare and look for problems in her, in the placenta, and in the unborn foal. The use of ultrasound has greatly helped equine veterinarians evaluate the placenta and equine fetus prior to birth. Problems with the placenta, such as placentitis and premature separation of the placenta, as well as fetal distress, can be recognized via ultrasound and steps made to correct the problems that would otherwise have been unknown.
If placentitis is suspected, then treatment with antibiotics will be instituted immediately. If, however, a foal arrives unexpectedly premature, without any warning, your veterinarian should be summoned immediately. In the meantime, keep the foal warm and dry. Save the placenta for evaluation by your veterinarian.
If the foal is delivered via cesarean section or if labor must be induced due to sudden severe injury or illness of the mare, then the foal will be evaluated by your veterinarian and the degree of immaturity assessed. At that point, the decision can be made as to prognosis for survival, whether or not the foal will require intensive care, and what type of complications might be expected. An appropriate facility that has a neonatal intensive care unit is, of course, mandatory for a successful outcome, so discuss the options in your area with your veterinarian. (See table of neonatal intensive care facilities in The Horse of January 1999.)
- Lester, G. and Koterba, A. "Prematurity." Current Therapy in Equine Medicine, 4th ed. Philadelphia, W.B. Saunders. 1997. pg. 586-589.
- Koterba, A. M. "Prematurity." Equine Clinical Neonatology. Philadelphia, Lea & Febiger. 1990. pg 55-65.
- Koterba, A. M., and House, J. K. "Prematurity." Large Animal Medicine. Philadelphia, Mosby. 1996. pg 354-359.
About the Author
Christina S. Cable, DVM, Dipl. ACVS, owns Early Winter Equine in Lansing, New York. The practice focuses on primary care of mares and foals and performance horse problems.
POLL: University Equine Hospitals