Early Signs?   Although normal gestation in a mare is considered to be 340 to 342 days, some mares routinely deliver their otherwise full-term foals up to a week or more early, while others deliver two weeks late.
   "There is some variation in 'normal' gestation" says Walter Zent, DVM, former president of the Society for Theriogenology, and a practitioner for some 40 years at Hagyard Equine Medical Institute in Lexington, Kentucky, where he limits his practice to reproduction. "As long as the mare carrier for more than 330 days, you needn't worry too much about it."  Much earlier than that and you should be concerned, even if the newborn initially appears healthy.
   Spontaneous abortions far outnumber premature deliveries, and the causes of abortion are many.  In contrast, premature births occur occasionally (Zent sees about a half-dozen cases a year among his 500-mare caseload), and the early births are nearly always brought on by placentitis (infection of the placenta).  "The most common kind is 'ascending placentitis," explains Zent, "meaning the infection starts at the cervix and moves forward. Nocardioform placentitis is another type of placental infection, although it's less common, it starts down in the body of the uterus at the base of the horns."
   Vaginal discharge is a common sign heralding ascending placentitis.
   Other factors occasionally increase the risk of premature delivery.  They include an incompetent cervix, a compromised uterus that is unable to properly support the enlarging fetus, and twins (which occasionally get missed in exams).  Toxins and disease can rarely cause premature deliveries.
   "If the mare has something that makes her very, very sick, usually the foal becomes sick and dies, then is aborted as opposed to being a premature birth," Zent states.

Consequences     Owners usually have few advance clues that their mares are going to deliver early, though signs of mammary gland development or vaginal discharge might preced pre-term birth.
Zent says, "Often, by the time mares start showing outward signs, the underlying conditions have created so much placental damage it's difficult to do much about it.  Odds are you'll get a very weak foal that's going to take pretty intensive medical care to survive.  Still, some premature foals are not infected by the organism that caused the placentitis, and do survive."
   In cases where the mare does show signs of early labour, the veterinarian should be notified right away.
   "If the mare has a discharge and her cervix is open, the vet can culture her and treat her with appropriate antibiotics and other therapeutic agents and sometimes you win - we get a healthy foal," Zent says.  "The vet can use ultrasound to look at this area, perhaps see how much placenta separation there is, and assess the situation."  In the event of an early birth, it's important that the veterinarian examine the placenta.
   "There's a lot of good information that can be gathered from the placenta that may help to determine the cause of the premature delivery," notes Zent.  Fortunately, most mares don't require special postnatal care.
   "Delivering early may not pose a risk for future healthy pregnancies or deliveries," Zent says.  "In fact, the delivery is usually pretty easy because the foal is small. The risk is a little higher for the placenta not coming out or leaving on horn in the uterus, so that does need to be checked.  If that happens, the mare could develop a uterine infection, from which there could be serious consequences."
   While most foals can be expected to have healthy, normal futures without extra veterinary attention, the preemie foal is usually not so fortunate.  These youngsters are often born with incomplete bone formation and immature organs.  Thus they are at an increased and often significant risk for respiratory problems, colic and gastrointestinal disorders, sepsis, limb deformities, muscle weakness, hypthermia, hypoglycemia, diminished suckle refles, and ineffective swallowing.  At maturity, they often remain undersized, lack athletic ability, and have chronic problems.

Preemie Prognosis   The  outlook for the premature foal depends on its gestational age , cause of early birth, neonatal condition, and the speed and quality of the supportive care it receives, explains Karen Wolfsdorf, DVM, a practitioner/partner at Hagyard specializing in reproduction.  Odds decrease considerably for foals born before 300 days.
   "They usually have a very poor survival rate, even with a lot of intensive care," says Wolfsdorf.  "If they do survive, they ususally have such serious, lifelong health and soundness problems that it's considered impractical to try to save their lives."
   In the event of a premature birth, owners should first make sure the foal is kept warm, then summon the veterinarian, advises Wolfsdorf.  Newborns incapable of rising or nursing should be examined immediately.  Foals that are getting up on their own and are nursing should be seen within four to six hours, even if they appear to be normal other than their small size.
   "The bigget mistake is not seeking veterinary help early enough," states Wolfdorf.  "The foal is going to look its best at birth or soon after it's born, but many start to decompensate 24 to 48 hours later and spiral downward.  You want to have tht foal assessed and started on the appropriate therapy so it won't become more compromised."
   To evaluate the foal and its chances, the vet begins with a history of the mare.  Wolfsdorf asks, "How far along was she when she delivered?  Did she have any signs of premature delivery beforehand or did she just deliver prematurely without any kind of warning?  These answers will give me an idea of what to expect and how I'm going to approach theis foal."
   Wolfsdorf says an important factor is that foals stressed in utero are usually much more developed than foals that have not been stressed, so the presence or absence of signs of pre-term birth are meaningful.
   "The stress produces an increase in cortisol release," Wolfsdorf explains, "which causes advanced maturation of vital organs such as the lungs.  This stress may be the presence of placentitis, sickness in the mare such as colic or endotoxemia, or any other situation that is ongoing."
   After collecting mare history, the vet examines the foal.
   "Their appearance, mentation (mental activity), and how they're acting will really determine what I do next,"  Wolfsdorf states.  "Can the foal get up on its own, is the foal nursing, does it have a suckle reflex?  Does it have a shiny, thin coat and floppy ears, which are signs of premature development?  Are its bones completely ossified?  I then try to cateforize the foal into one of three groups: critical, stressed in utero but fairly normal, and middle-of-the-road." 
Critical: The critical foal is very weak and suffering from multiple system failures.  This newborn is unable to rise or lift his head and lies on his side, gasping for oxygen.  He's usually septic and often in shock.
   "Most of the critically ill foals are from mares that have shown no signs of impending delivery,"  Wolfsdorf says.  "Because his organs may not be completely developed and functioning properly, he's going to need oxygen and extensive supportive hospital care to survive," including plasma transfusions to bolster the immune system, significantly increased nutrition, and orthopedic supports such as splints or casts.
   Hospital stays usually last at least a couple of weeks, or sometimes longer, so treatment can be costly.
   Additionally, these foals have a lower percentage of survivability, and if they do survive, performance is unlikely to meet expectations.  Consequently, the decision to treat becomes a matter of intended goal, practicality, and financial wherewithal.
Stressed:  The foal that's been stressed in utero is a little small and weak, but it can get up and nurse and behaves pretty much like a normal foal, Wolfsdorf says.
   Supportive care, such as meeting nutritional and immunological requirements, administering preventive antibiotics, and identification of ossification of bones, can be performed on the farm.
Middle-of-the-road:   The middle of the road foal is a little weak and doesn't have much of a suckle reflex, but it is bright, attemps to stand up, and can be assisted up.  These foals can also be treated on the farm.  Supportive care is often directed at helping them gain strength and preventing sepsis or other complications from occurring, such as insertion of a nasogastric tube to deliver nutrition, administration of fluids to prevent dehydration, supplemental plasma to bolster the immune system, antibiotics to ward off infection, use of heat lamps for warmth, and allowance of limited exercise while bones complete their formation.
   The outlook for the latter two groups is generally pretty favourable. Wolfsdorf states, "With supportive care and time, these foals can continue to do well.  They may be smaller than the others in the beginning, but a lot of them can grow to their full potential.

Prevention   Maintaining a good health program throughout the mare's pregnance (appropriate nutrition, vaccinations, deworming and regular exams) has been the primary means of improving the odds for a normal, full-term delivery.
   But within the last five or six years, Zent says, some vets hae started performing transrectal ultrasound exams of the placenta in order to detect signs of early placental disease.  "We examine the mares at the cervical star (the area of the placenta that is up against the cervix), " he says. "That's where you start to see lesions with ascending placentitis.  We think we have managed some mares with beginning placentitis by routinely looking at them, catching the problem when it starts, and treating them with antibiotics.  We check high risk mares at about 150 days getation, then every 30 days.
   Most vets are able to perform a rectal exam.  If they see abnormalities, they should summon a specialist for further evaluation and treatment.
   "Treating early placentitis is a pretty big learning curve, although anyone can take a look," Zent says.  "But we think this early ultrasound exam is worthwhile.  We hope we can catch the starting placental disease early enough that we can do something about it before it destroys so much placenta that it affects the growth of the foal:  If enough placenta gets destroyed, you're not going to have much of a foal even if he comes out alive."

Take-Home Message   Watch pregnant mares for signs of discharge or other problems that might complicate pregnancy.  As far as dealing with the preemie itself, the only preventive tactic is swift, preemptive veterinary attention.
   Stresses Wolfsdorf, "Prematurity is a serious condition, and it's important to get help early.  Most of the time, premature foals look their best when you first see them, but usually they'll get worse before they get better.  You need to start on these foals early.  If you provide these foals with good supportive care immediately, you'll improve their outcome."