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STILL LIFE: NOT A PRETTY PICTURE - Abortion & Stillborn foals 

One of the most difficult phone calls a stud master has to make is informing an owner that his/her mare has aborted … especially in later pregnancy when the anticipation of the expected foal is only around the corner.

After the initial “is she (the mare) ok?” nearly always the second question is “what was the cause?”

Quite often an accurate answer at that point in time can not be given. For this reason I am writing this article as a reference for those of you that get that call. My usual response to the difficult question is “you probably know someone who has had a miscarriage, even on the first pregnancy is common, and so it is with animals too”.

In reality I have not answered the question at all, it just puts in perspective the fact abortion is not uncommon, and does and can happen as a matter of course. These mares are a percentage of the population whose body evicts a foetus that is not quite right due to abnormalities: the result of infectious invasion, multiple pregnancies, poisoning, or a uterus that is not capable of sustaining a foetus due to age and wear and tear. And, to a much lesser extent than people would like to believe, trauma and emotional stress. The truth of it is, most will never know the cause in the end.

foal abortion mare early 93 days oldAny death of a pregnancy from 0-30 days old is referred to as Early Embryonic Death. The term Abortion is applied when expulsion of a foetus occurs after 30 days of age until 300 days. Any foal that is born prior to 300 days of gestation is regarded as unviable, hence the cut off for this expression. Stillborn (and, if alive, premature) applies to a lost pregnancy during the period of 300 days until full term of gestation of 340 days.
(Photo Right: a foetus of 93 days old. We were just lucky to catch this abortion occurring and quickly grabbed the camera!)

Definitions used in this article:

Placentitis - inflammation of the placenta.
Endometritis - inflammation of the endometrium.
Endometrium - the membrane that lines the uterus wall.
Chorion - The outermost layer of the placenta (red side of placenta that is in contact with the uterine wall) that is full of blood vessels spread across this layer and the location of the villi.
Villi - millions of very tiny finger or hair-like structures that “plug into” depressions in the lining of the uterine wall. This forms the support system of transfer (gas, waste and nutrient exchange) between foetus and mare blood streams.
Premature placental separation - when the placenta detaches from the uterine wall before the foal is ready to be actually born. This will leave the foal without the support system it requires and is exposed to asphyxia.

About Abortion
With more advanced pregnancies of 7-10 months abortion can be quite hard on the mare due to the foal's significant size. Very few mares at this stage give us indications of impending abortion as they are probably in the herd and are discovered after the event. As the abortion generally occurs spontaneously as far as she is concerned (infection may have been at work for a period of days or weeks, but the actual foetal expulsion is sudden) the mare’s body has not had the opportunity to prepare for the large body to be delivered as she would during normal pregnancy.

In other words, her cervix will be probably very tightly closed and her pelvic region has not had time relax, the vagina, vestibule and vulva will all still be “tight”. Those mares with a caslick will be foaling through an even smaller hole, causing ripping of the vulva. On top of all of this, the foetus unlikely to be in a normal presentation position and will deliver the foal whichever way it is coming out. Being typically female, other mares want to know what’s going on in their friend’s life. When abortion occurs many of these mares become over interested wanting to get a close look at the foetus. The poor mare that has aborted is not hormonally or behaviourally prepared and not only has to deal with the physical side of the trauma, now she will have to deal with all their busybody friends wanting to get close to the foetus, whist she is still trying to determine why her foal will not move and basically what in the hell just happened to her. (This behavioural factor is significant when discussing EHV1 later in the topic).

The Stillborn Foal
In the later period of pregnancy, it is much more likely that there are visual indications that a mare may have a possible stillborn or premature foal coming along. The mare may start to bag up or even be running milk prematurely, have a little bit of either bloodstained or puss-like discharge from the vulva and may be displaying discomfort. These kind of warning signs allow us to possibly avert a stillborn foal or reduce the extent of infection of the foetus through treatment regimes such as broad spectrum antibiotics, use of Sulprim, Regumate and anti-inflammatory drugs as per prescribed by the veterinarian. The mare should be placed under 24 hour observation, and if you don’t have that facility yourself, get her somewhere within striking distance where there is: one that is, preferably, able to deal with emergency foaling and supportive therapy immediately at hand (by that I mean intensive care unit and highly capable personnel – most of the issues need to be resolved well before a vet has time to arrive). In the last 30 days particularly there is still a good opportunity to have a viable foal, although it may well be born septic (infected) and, pending extent of infection, it could still have a very good chance to be saved, with a reasonable prognosis in the longer term to be a normal healthy foal.

This is the period where I feel there is a lot of conjecture and misrepresentation of the term still born for two reasons:

1) During this period it is regarded that the foal has the ability to survive at or after 300 days of gestation. In the real world there are very few foals that are capable of survival under 310 days, and those that do (after heaps of money and intensive care), are very likely to have undeveloped organs and ongoing problems: particularly proper ossification (hardening) of the carpal bones (knees) and/or hocks. Quality of life for the foal may be a very real consideration when confronted with a very premature foal. Personally, I think we have a more realistic chance of salvaging a foal from 30 days (310 days) prior to due date.

foaling  premature placenta separation red bag foaling 2) Stillborn foals do happen, but the term is loosely used for any foal found born dead. The definition may also be unfairly used for foals that died during the delivery process. In reality, these foals are often lost when there is inadequate knowledge and facility to deal with emergency procedure for a problem such as premature placental separation, not acting upon a slow and difficult delivery, or worse: not being there at the foaling. With very good early observation of a premature placental separation, experienced personnel with above average husbandry skills and a facility to deal with emergency procedures during the delivery and immediately after birth, many foals are saved in the first hour of their lives. Infection may end up beating us in the long run, but at least we have a good sporting chance of saving these foals. Percentages of stillborn foals are significantly reduced when these superior conditions are available.

(Photo Right: Premature placental separation that resulted in a live foal due to good early observations of the presentation of a “red bag” and speedy work at and after foaling. Note that the umbilical cord is still attached to the foal, and the placenta immediately followed the foal out at parturition. These signs indicate premature placental separation. In this case the foal did not appear infected, but was covered with antibiotics all the same.)

The Live Premature Foal
These foals are again 300 days and over and born alive (there’s that 300 again I hate so much!). This will include the “stillborn candidates” mentioned above of course.

It must also be remembered that normal gestation can go well beyond 340 days (to say 370 days), so in reality you can have a dysmature or 30 day like premature foal at the mare’s due date. This is an extreme example, but think about it for a minute! We see plenty of foals born over their due dates with premature features such as a domed forehead, floppy ears, generally undersize and fine boned. We must remember that the 340 day gestation period is based on a historical average. Be aware that a dysmature or premature like foal may indicate a problem.

For the very premature foal I would recommend the inexperienced owner ask the vet a very direct question regarding the feasibility of keeping the foal alive, weighing up most importantly the humanity of going ahead with the foal, costs of getting to a healthy foal, time commitment required, expected recovery time and, at the end of the day, real viability of the foal at face value. Some of the very premature foals should simply need euthanizing on humane grounds.

Those born in healthier circumstances are more the point of topic here. Prematurity is most likely to be a result of other contributing factors, the most common being infection. For those “healthy looking”, but small premature foals should still be viewed as being born with a predisposing infection. An ugly, thickened and or discoloured looking placenta is a sure give away that there is an underlying problem, and a vet should be called immediately. Bloods will likely be taken and covering antibiotics would probably be prescribed. Many premature foals will need good nursing such as hand feeding or stomach tubing including supplemented colostrum, aid in standing, warmth and maybe supportive fluid therapy, including supplemented colostrum and possibly plasma. This is quite a commitment for the small owner financially, time required and emotionally. As these foals are born alive there is a very strong emotional attachment with the premature foal.

Reasons for abortion, stillborn and premature foals
There are quite a few reasons for abortion, but many only contribute to a very small percentage of incidence. Potentially EHV-1 can be the biggest cause of abortion, and in a year where outbreak occurs in a region of high concentration of horses, can significantly escalate total abortion numbers in the equine population as a whole: particularly during periods of stress, such as drought. However, since vaccination has become widespread, it now comes in at second place as the major cause of abortion behind placentitis.

Infectious Causes :

Viral Infections:

EHV-1 (Equine Herpesvirus 1, Rhinopneumonitis): Due to the highly contagious nature (with dramatic results), EHV-1 has to be considered the most important cause of abortion, warranting full attention by the equine community to work on preventing the spread and diagnosing or eliminating its occurrence when confronted with an aborted foetus. The virus spreads by ingestion or inhalation and, once contracted, invades the placenta and attacks her foetus, which becomes infected with abortion usually occurring 3-12 weeks later. Generally the mares do not show signs of illness, and to the owners it appears as a spontaneous event. Most abortions occur during the last part of gestation from 8 months on, but should not be discounted as a cause from 5 months onwards. Some foals are born with the virus and die soon after. The problem is the virus can lay dormant in a host animal, and during a period of duress it can manifest and cause a new outbreak in a susceptible population.

I’ll now revisit a statement made earlier about mares often congregating around an aborted foetus; this is very worrying should this foetus be a result of EHV-1. It is most important that mares ARE NOT MOVED as they are already exposed to the virus by the time you find the foetus. When we first started out, abortion “storms” were the common result of EHV-1 outbreaks where 80%, even 90%, of the pregnant population within a farm, or even a group of neighbouring farms, would abort their pregnancies. Vaccination programs have impacted very positively reduce the incidence of Equine Herpesvirus 1.

Contagious Equine Metritis (CEM) & Equine Viral Arthritis (EVA): both will result in abortion, although mares with CEM are unlikely to conceive. They are both quite uncommon but worth mentioning.

Bacterial infections:  The usual suspects have appeared again! These guys just keep appearing and have been discussed, at length in another feature, as causes of sub fertility or infertility. Most result in placentitis which kills by scarring or grossly inflames the chorion so the villi on the placental surface “break away” or “let go” from the endometrial lining. Often these pregnancies will go close to term, but are often associated with premature placental separation. Many true stillborn foals are a result of premature separation.

foal abortion mare foetus 4 months Streptococcus; mainly Strep. zooepidemicus: in this case the placenta becomes infected (placentitis). The placenta becomes thickened at the site of infection and when it becomes widespread, or chronic, it will starve the foetus and result in abortion usually at 3-6 months of age. The placenta will be grey and thickened in large patches and may also have patches of healthy placenta.
(Photo Right: A 4 month aborted foetus found in the paddock with the mare still standing over the site. The placenta of this abortion was as described here. Notice the umbilical cord has separated from the placenta. We had to manually remove the placenta from the mare's uterus as it was still partially adhered to the uterine wall. This is not unusual with abortion)

Escherichia coli (E coli): is most common in the second half of gestation and will result in placentitis and foetal disease. The Chorion will appear an unhealthy, discoloured red /brown colour.

Klebsiella pneumoniae: although not as common, it is nasty when the mare becomes infected. Mostly she will not conceive, but if she does, this will nearly always result in abortion. As previously mentioned in the sub fertility article, the problem with this type of infection, is that it is quite harsh on the mare’s uterus and cervix, impacting strongly on her resistance against other organisms and difficult to get rid of it.

Pseudomonas aeruginosa: causes placentitis and often results in abortion, which is noted by a dark red cervical star of the placenta, discoloured allantois (the white inner sack) and grey and dead looking parts of the chorion.

Fungal infections (Mycotic infections): generally it is thought the organisms enter via the bloodstream, via the gut or lungs, to the placenta, causing placentitis and often resulting in abortion. Again the placenta is thickened and covered in brown, sometimes shale-like material. These aborted foetuses will be undersize due to starvation.

Placental abnormalities:  Placental abnormalities can be a cause of abortion in itself.

Umbilical cord torsion and cord length: a torsion (twisting) of the umbilical cord will starve the foetus and is often blamed when there is no other obvious explanation. The cord naturally has twists in it, but should there be local swelling and discoloration, then it will probably be to blame. Overlong and extra short umbilical cords can also be a problem. Short ones can rupture prematurely and extra-long ones, getting over the 80 cm mark, often result in abortion. I have a case history with photograph of a full term foal still born foal with an extra long cord.

Incomplete development of the Chorion villi: will often result in Premature Placental separation but is more usually the effect from infection. When the villi do not develop in the normal way, then they will either fail to attach to the uterine wall and again, starve the foal. This is seen more often in older mares.

Hormonal: progesterone levels may dip at the time when the placenta takes over from the corpus luteum of progesterone production. This is unlikely to be diagnosed, and will happen under 100 days, so is often undetected.

Reproductive tract incompetence:  wear and tear resulting in scarring of the uterus will inhibit the job of the villi, resulting in low nutrient absorption and starve the foetus. An incompetent cervix and poor perineal tone can lead to a pregnancy loss. These mares would be great candidates for embryo transfer as they are quite capable of becoming pregnant, but only once the embryo is exposed as it enters the uterus. Embryo transfer removes this embryo very soon after migrating into the uterus and is implanted into a recipient mare.

Foetal abnormalities:

Chromosomal: more likely to result early in pregnancy with most occurring under 100 days.

Other genetic or developmental abnormalities: as with humans, foetal deformities, including physical (skeletal), organ abnormalities and immunity disorders, occur and are a percentage of loss. Gross deformities may be aborted, but quite often they are born alive and those with physical deformities are often euthanized on humane grounds. Foals that are born alive with organ deformities often die soon after birth, or may be also euthanized, pending on the problem.

Bacteria and Toxins:

The hairy caterpillar (Eastern Tent caterpillar) is a relevant example in
some parts of Australia. Found in areas where there are box eucalypts, white cedars and acacia, the caterpillars are inadvertently ingested, whereby their barbed hairs embed into the mare’s digestive lining. This damaged lining exposes the mare to bacterial invasion that can migrate to the foetus and placenta. Abortion occurs about 10 days after exposure.
Some toxic weeds or grasses are thought to cause abortion.

Insecticides and weed poisons need to be carefully considered around the pregnant mare. The paddocks should not be stocked during, or for a period after, spraying (refer to individual instruction).

Embryonic location or multiple pregnancies:

Uterine body pregnancy: This is when the pregnancy implants either in the body of the uterus or at the junction of the uterus and horns – a normal pregnancy develops in one horn of the horse uterus. Basically there is not enough room for the foetus to continue growth and is expelled. Looking at a placenta, both horns are small and visually of a similar size, determining that this has occurred.

Twins: abortion is the most likely outcome of a twin pregnancy. Should the pregnancy advance to live birth, then quite often one or both will be destroyed as they are rarely big enough to survive. On the odd occasion a reasonable sized foal is produced and the second twin has mummified at an early stage, and comes out with the placenta. Twins used to be a relatively common occurrence prior to the ultrasound scan, and I’ve seen a few mummified foetuses’ (unfortunately I did not have the foresight to photograph this at the time). We have not seen a set of twins for a number of years, but that is not to say they haven’t occurred and been aborted in early stages of pregnancy when abortion may have gone unnoticed. Twins are more prevalent in particular breeds, and in mares that do not experience the intensive early ultrasound pregnancy testing regime of the thoroughbred.

Illness, temperature and pain from injury: When a mare becomes sick with high temperatures she is exposed to the possibility of abortion as body systems cannot cope outside a normal temperature range. Physical pain is thought to contribute to some abortions.

Stress & Trauma: Both emotional stress and physical trauma do not contribute to abortion statistics anything like as often as you might think, but is often blamed when owners need an answer as to why their mare aborted. The foetus is very well cushioned inside the uterus, encompassed within fluid sacks, so it would take and almighty kick in the right place to cause abortion. This may be verified with a bruise on the foetus.

foal abortion mare foetus 9 months oldNutrition:  A mare experiencing very low nutritional levels may abort as a natural way to ensure her own survival. Lower body weight or weight loss during pregnancy will alter the conformation of the perineal region, and in turn exposing the mare to infectious invasion to her reproductive tract.

(Photo Right:  An abortion caught prior to the event was occurring. In this case the mare was attended and the dystocia corrected prior to delivery making the whole process much easier on the mare. This is a 9 month foetus)

Reducing incidence of abortion and stillborn foal:
Reducing the incidence of abortion is largely common sense, and most of the factors below should be deduced as to what the causes are:

  • Good pregnancy diagnostics, especially with twin diagnosis.
  • Good hygiene practises when reproductive work is being performed.
  • Vaccination programs, especially EHV1-4 during pregnancy should be practiced.
  • Quarantine pregnant mares arriving on the farm for a good month, to reduce risk of spreading disease.
  • Provide good nutritional standards and be aware the last 1/3rd of gestation is when the foetus really accelerates in growth rates.
  • Do not drench the mare in the last month of pregnancy and always read the label before drenching any pregnant mare.
  • Have well sheltered paddocks for pregnant mares – prolonged and extreme cold weather/ heavy rain periods may cause abortion. We feed out extra lucerne during those periods.
  • Ensure the mare’s vulva has a caslick if required, or does not become sloped during pregnancy. If so, stitch her up mid pregnancy – it won’t hurt.
  • Diligent daily inspections of the mare for health, premature udder development or possible abortion having occurred. Keep an eye out for vaginal discharge. A pregnant mare standing away from a herd is always suspicious.
  • Sensible handling of the horses and take care not to yard too tightly together.
  • Be responsible if spraying pastures with chemicals – check the time frames on the product information in which the pregnant mares may return to that paddock.
  • In the case of a habitually aborting mare, her abdomen may be scanned during pregnancy to monitor indications of placentitis and introduce a drug program to help maintain this pregnancy.
  • If the mare bags up prematurely, get veterinary assistance (regular scanning and monitoring, noted above, may be implemented as well).
  • Simple: don’t buy mares with a poor history of not carrying pregnancies to term.

Plan of action when abortion occurs:
1) DO NOT move the other mares in the group! All abortions must be considered infectious until ruled out, and the herd is already exposed by the time the aborted foetus is found. Leave everything as is and go back and call the vet and let them know where you will have the mare when he/she arrives. Collect the following items:

  • Extra help: removing the mare can be difficult in a herd situation and needs two people.
  • Change into gumboots (easier to clean down later) and disposable gloves
  • Large garbage bag or something waterproof in which will hold foetus & membranes (wheelie bin garbage bags are good for this).
  • A bag of lime.
  • Headstall & lead.
  • A vehicle with a tray.
  • At the place where the mare is being moved to have sterilising baths for sterilizing gumboots, equipment and the vehicle tray. Extra smaller garbage bags may be handy also for disposal of product and equipment that has been contaminated.
  • If this is a herd, there is a very good chance that curious mares will be a great nuisance and can even be dangerous. As quickly, and with as little as fuss as possible (so as not to attract their curiosity), get the foetus bagged. Dump the lime there and get both the mare and the foetus out of the paddock. Get the mare relocated to a place of isolation that is capable of holding her for a period of time: preferably somewhere she can be inspected internally by the veterinarian.

2) If the other mares in the herd are not a problem, lime the area thoroughly where the abortion occurred, otherwise park the vehicle carrying the foetus away where from any horse contact and return to perform this duty. Keep the foetus on the vehicle tray – it is easy to sterilise and is a great examination bench for the vet. Wear disposable gloves.

3) Understand that all handlers are now quarantine themselves and should be aware of this. They must not handle any stock or equipment that may come into contact with mares outside the contact group.

4) Once the veterinarian has arrived, and examining of foetus and mare have been performed, they are now your primary source of advice on further risk management and protocol for care of the mare. It will be totally dependent on the findings of this examination, and hence reinforcing the importance that such consultation has taken place.

The truth is, most abortions go undetected, as they happen in the earlier stages of pregnancy. These are discovered well after the event, when the so called “pregnant mare” does not look as pregnant as she should, and a pregnancy test is performed confirming that suspicion. For later abortions the foetus should be sent off to discount EHV-1 as being the source of the problem. Frankly, I don’t think it is worth the trouble nor expense to perform further diagnostics once EHV-1 has been eliminated as over 50% of the cases will be inconclusive.

If the time of the season is relevant I would place the mare that aborted under lights. Many of these mares will not follow normal wet mare cyclicity (that is foal heat, and cycling thereafter) and they may suffer a set-back due to pain and appetite loss after the physiologically traumatic event, which again may “shut them down” temporarily. Light therapy is a good way to address most of the problems associated with the mare that has experienced an abortion in the mid to later (6-10 months) stage of pregnancy. I always feel it is important to get the mare back into a good size social group as soon as possible as they seem to return normality much quicker.

For mares that have aborted I would make sure she had a uterine swab done on her transitional or first detected heat. If the cause of abortion was the presence of bacteria, then this - with sensitivity analysis done – the offending bacteria can be tackled head on. In the older mare and/or mare whose inability to hold pregnancies is becoming suspicious, I would consider getting a uterine biopsy done for a “snapshot” of the mare’s uterine endometrial condition (inflammation, degree scarring, and glandular swelling). I would also ask for a manual “feel” of the cervix and other reproductive tract areas along with a speculum during estrus to check for possible urine pooling. It is likely an internal vaginal inspection will have been performed post abortion, but revisiting this on her first heat would be prudent to ensure all is in order before breeding the mare.

A considerable number of mares will slip, abort or have a stillborn foal at least once or twice in their reproductive life and it is still considered as a “normal” percentage. After all, none of us are likely to ever be the owner of a mare like Lady Violet. Lady Violet has had 18 foals straight without a single miss, slip or abortion. All the foals except one (just turned 3 years old last month) have been named, so they also survived long enough for that distinction. The date of birth of her first foal was 8th September and her 18th foal was born on 14th October, losing only 36 days across that whole period!

Not only that, Lady Violet produced the Group One VRC Salinger Stakes winner, Notoire (also winning the Group Two Schillaci Stakes and two other stakes events) and multiple Listed winner Well Known.

Just an incredible mare … and one, given the topic of this feature, that we can only but dream about.

Related Stories:

No One Home: Causes of Infertiltiy and Sub-fertility in Mares

Extra Long Umbilical Cord

© Christie Woodard and “Still Life: Not A Pretty Picture - Abortion & Stillborn foals”, 2014
Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Christie Woodard and “Still Life: Not a Pretty Picture - Abortion & Stillborn foals”, and a link specifically directing to the original content. 

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