Identification and Management of the High-Risk Pregnant Mare

IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE

Identiﬁcation and Management of the High-Risk Pregnant Mare

Margo L. Macpherson, DVM, MS, Diplomate ACT

Conditions threatening pregnancy in late term mares can pose unique challenges to the practitioner. The following manuscript reviews clinical scenarios that the equine practitioner may encounter with late pregnant mares. Diagnostic and treatment options are also discussed. Author’s address: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, PO Box 100136, Gainesville, FL 32610; e-mail: [email protected]ﬂ.edu. © 2007 AAEP.

1. Introduction foaling. Parity can affect the timing of mammary- Several conditions can jeopardize the pregnant gland development. Nulliparous (“maiden”) mares mare. The challenge that a practitioner faces is often develop mammary glands immediately before accurately identifying and resolving the condition foaling with little warning. Precocious develop- threatening either the life of the mare and/or the ment of the mammary gland occurs most often in fetus. Conditions contributing to pregnancy loss in mares with twin pregnancies or bacterial placenti- the late-pregnant mare include infectious agents (vi- tis. Premature mammary-gland development is a ral, bacterial, and fungal), twin pregnancies, fetal or sign of impending delivery and usually occurs in the placental abnormalities, structural abnormalities last trimester with these conditions. Determining (hydropic conditions, ruptured pre-pubic tendons, or the cause of premature mammary-gland develop- abdominal wall herniations), and systemic illnesses. ment is essential when formulating a management The practitioner is most commonly presented with a plan for the condition. mare that (1) is not systemically ill but has premature udder development, (2) is acutely painful, or (3) History and Physical Examination has an unusual increase in abdominal size. The Several important historical points must be investi- purpose of this manuscript is to describe common gated when determining the cause of premature clinical scenarios in late-pregnant mares and review mammary-gland development in the mare. management options for these conditions. How Was Early Pregnancy Diagnosis Determined 2. The Mare With Premature Mammary-Gland in This Mare, and Was She Examined for Twins? Development A thorough history can be particularly useful when One of the more common medical complaints of differentiating mares with twin pregnancies from mares in late gestation is premature mammary- mares with bacterial placentitis. Information gland development. For the “normal” foaling mare, about methods for early pregnancy diagnosis, previ- udder development typically occurs 2–4 wk before ous history of twin pregnancies, conﬁrmation of dou-

NOTES

AAEP PROCEEDINGS ր Vol. 53 ր 2007 293 IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE ble ovulations, and presence of twins during initial If vulvar discharge is present, a swab for bacterial pregnancy examinations can support ultrasono- culture and antimicrobial sensitivities should be ob- graphic findings in the late-pregnant mare. With tained. A direct swab from the discharge at the the advent of early ultrasonographic diagnosis of vulva is useful for screening purposes. A vaginal pregnancy in the mare and the successful twin- speculum examination should be performed, and an crush technique, twins rarely survive to late gesta- additional swab should be taken from discharge tion. However, as a result of better diagnosis of noted in the cranial vagina or at the external cervi- twins in early pregnancy, one can easily overlook cal os. These samples may provide a more defini- twin pregnancies as a cause of premature udder tive identification of a specific organism if obtained development in the late-gestation mare. In some under aseptic conditions. Swabs from the cervical cases, an ultrasound is not used to determine preg- lumen or uterus would be contraindicated, because nancy in the mare, or ultrasonographic examina- penetrating the cervix poses a high risk of disrupt- tions were performed early (i.e., day 14), and twins ing the pregnancy. were not detected. When twins are not detected, later examinations are often performed with manual Is the Mare Systemically Ill? palpation of the reproductive tract only, which Mares with twin pregnancies or bacterial placentitis would detect a twin pregnancy. rarely show signs of systemic illness. Baseline parameters (temperature, pulse, respiration, gut How Long Has the Mare Had a Precociously sounds, and digital pulses) do not typically fall out- Developed Mammary Gland, and Has She Been side of normal limits with these conditions; this may Streaming Milk? be indicative of gastrointestinal crisis or systemic illness such as endotoxemia but not twins or bacte- Although these questions will not necessarily help rial placentitis. differentiate between twins and placentitis, it gives perspective as to the duration of the problem. Transrectal Palpation and Ultrasonographic Mammary-gland development and associated signs Examination often occur well into the disease process in the mare Transrectal ultrasonography in late gestation is pri- with placentitis. Mares carrying twins tend to marily useful for evaluating placental integrity at acutely develop a mammary gland in preparation for the cervical star, fetal-fluid character, and to lesser delivery. Rapid assessment and implementation of extent, the fetus (i.e., activity and orbit diameter). treatment is essential in these mares. Both mares Examination for twin pregnancies in late gestation with placentitis and mares with twins that develop a using transrectal ultrasonography is highly unreli- mammary gland are imminently at risk for prema- able. Only a limited portion of the uterine contents ture delivery. Loss of important colostral immuno- is seen using transrectal ultrasonography. globulins may impact survival of the prematurely The most frequently affected area in mares with delivered neonate. Secretions streaming from the bacterial placentitis is the caudal aspect of the al- mammary gland can be passively collected from lantochorion near the cervical star. Therefore, mares and frozen. Determining an outside source thorough examination of this area is critical when of colostrum or plasma are also good precautionary diagnosing placentitis. In the normal pregnant measures for mares with these conditions. mare, the area visualized in the region of the cervical star is the combined uterine and placental (cho- Does the Mare Have a Vulvar Discharge? rioallantoic) unit. Renaudin et al.1,2 developed the Vulvar discharge is a symptom of some mares hav- technique for evaluation of the combined thickness ing bacterial placentitis. However, this is not a of the uterus and placenta (CTUP) and established hallmark sign of bacterial placentitis, much to the normal values in light-horse mares throughout ges- surprise of many practitioners. Mares may have tation. Serial evaluations of the CTUP can also be fulminate placentitis as evidenced by placental useful for monitoring progress of disease and/or re- changes seen with transrectal ultrasonography, but sponse to treatment. they may not have visible vulvar discharge. Con- The procedure is relatively easy to learn, but it sequently, vulvar discharge is a sign that can be does require practice when establishing reference unreliable when attempting to differentiate the points. Fecal material is completely evacuated mare with placentitis from the mare with twins. from the mare’s rectum. Minimal manipulation of When present, discharge is most often purulent to the reproductive tract reduces stimulation of the mucopurulent, and occasionally, it contains bloody fetus. A 5- or 7.5-MHz linear transducer is placed material. Small amounts of discharge may accu- in the rectum and positioned 5 cm cranial to the mulate on the vulvar lips only to be swished away cervical-placental junction. The transducer is with the mare’s tail. Careful examination of the moved laterally until the large uterine vessel (pos- tail and perineal area may reveal evidence of dried sibly the middle branch of the uterine artery) is material on the buttocks or tail of the mare. Mares visible at the ventral aspect of the uterine body.2 having twin pregnancies rarely have vulvar dis- The CTUP is measured between the uterine vessel charge unless they are in the process of aborting. and the allantoic fluid (Fig. 1). A minimum of three

294 2007 ր Vol. 53 ր AAEP PROCEEDINGS IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE

Fig. 1. The CTUP is measured using transrectal ultrasound on day 304 gestation in a normal, pregnant mare. Average measurements from this mare were 8.5 mm. The normal reference value for this stage of gestation is a CTUP measurement Ͻ 10 mm. measures should be obtained and averaged. In- creases in CTUP of Ͼ8 mm between days 271 and 300, Ͼ10 mm between days 301 and 330, and Ͼ12 mm after day 330 have been associated with placental failure and pending abortion (Fig. 2).3 It is important to obtain all CTUP measurements from the ventral aspect of the uterine body, because physio- logical edema of the dorsal aspect of the allantochorion has been noted in normal pregnant mares Fig. 3. Edema in the dorsal aspect of the uteroplacental unit during the last month of gestation (Fig. 3).2 Phys- detected using transrectal ultrasonography. This ﬁnding is of- iologic edema of the membranes could be misdiag- ten normal in near-term mares. This image was obtained on day 323 gestation, and a healthy foal was delivered 5 days later.

nosed as pathological thickening of the fetal membranes. In addition, care should be taken to avoid including the amniotic membrane when mea- suring the allantochorion and uterus. Fetal pressure on the caudal uterus can falsely decrease the CTUP. Measures of the CTUP should be obtained when the fetus is not in the pelvic canal. Transrectal ultrasonographic examination can also be used to identify pockets of purulent material (hyperechoic) between the uterus and the placenta (Fig. 4). This ﬁnding is pathognomonic for placentitis. Measurements in cases with placental separation are meaningless. Transabdominal Ultrasonographic Examination of the Reproductive Tract Transabdominal ultrasonography is an excellent Fig. 2. Thickening of the CTUP is detected using transrectal tool for evaluating the fetus and placenta in 4–6 ultrasound. Average measurements from this mare were 10 mm mares. Fetal wellness can be assessed through at 293 days gestation. The normal reference value for this stage transabdominal ultrasonographic measures of fetal of gestation is a CTUP measurement Ͻ 8.0 mm. heart rate, tone, activity, and size. Placental-

AAEP PROCEEDINGS ր Vol. 53 ր 2007 295 IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE the uterus and confirm the number of fetuses.10 Using this method, both the pregnant and non- pregnant horns can be evaluated in their entirety, and the fetal number can be determined. As seen with transrectal evaluation of the normal equine pregnancy, the chorioallantois is intimately associated with the endometrium and cannot be easily identified as a separate structure from the transabdominal approach (Fig. 5). Mares with normal pregnancies should have a minimum CTUP of 7.1 Ϯ 1.6 mm and a maximum CTUP of 11.5 Ϯ 2.4 mm.4 Using this method, pregnancies with an increased CTUP have been associated with the delivery of abnormal foals.4 Evaluation of the caudal allantochorion is not accurate using the transabdominal approach. However, transabdominal evaluation of fetal membranes is very useful for identifying placental abnormalities in mares with hematogenously induced or nocardia-form placentitis. Mares infected with the nocardia-form bacteria will often have placental separation and purulent material at the base of the gravid horn and the junction of the 11 Fig. 4. This transrectal ultrasound image depicts a separation of uterine body (Fig. 6). The transabdominal ap- the chorioallantois from the endometrium in the area of the proach is the most accurate means for diagnosing cervical star. Note the accumulation of purulent material be- nocardia-form placentitis. tween the chorioallantois and endometrium. In addition to diagnosing placental disease, transabdominal ultrasonography is useful for monitoring fetal health. Fetal parameters such as heart rate, activity, and tone can be assessed using a transab- membrane integrity and thickness and fetal-fluid dominal approach. Determining fetal number in character are also evaluated using this technique. late-gestational mares is also most accurate using a Transabdominal ultrasonography is the most accu- transabdominal ultrasonographic approach. rate method to diagnose twins in late gestation. Locating a fetus(es) is most easily done by iden- For ideal examination, the mare’s ventral abdo- tifying the fetal thorax. The fetal thorax is visu- men is clipped from the mammary gland to the alized as several linear, hypoechoic shadows xyphoid process and up to the level of both stifles.7 (intercostal spaces) interdigitated with linear, hy- The area is cleansed of debris. Coupling gel or al- perechoic ribs. The active fetal heart is easily cohol is applied. In cases where clipping the ven- identified at the cranial most aspect of the fetal tral abdomen is not an option, thorough (and frequent) wetting of the abdomen with alcohol generally facilitates proper examination of the abdominal contents. Ultrasonographic examination of the equine abdomen should be performed using a 2.5- or 3.5-MHz transducer with a depth setting of 20–30 cm.4,5,7–9 Although a 5-MHz transducer can be used to measure fetal heart rates in late gestational fetuses, the limited tissue penetration of this transducer type precludes its use for the thorough examination necessary to detect twins or perform complete fetal assessment. All four quadrants of the abdomen should be systematically examined: right cranial, right caudal, left cranial, and left caudal. The initial examination usually begins just cranial to the mare’s mammary gland to ensure detection of a fetus as early as 90 days gestation. The abdomen is scanned in a sagittal plane through all four quadrants, because this is the most common orientation of the fetus (cranial or anterior position in the sagittal plane) late in Fig. 5. Measurement of the CTUP using transabdominal ultra- 7,8 gestation. Subsequent scanning in a trans- sonography. Measurements in this image are within normal verse plane is necessary to image all aspects of limits (Ͻ11.5 mm).

296 2007 ր Vol. 53 ր AAEP PROCEEDINGS IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE be difficult, because traditional landmarks, such as the heart, are often not beating and may be obscured by the limbs of the flaccid fetus. Serial examinations should be performed to verify fetal wellness or distress. Once daily transabdominal ultrasonographic assessments are commonly performed in high-risk mares. Fetuses experiencing distress are often evaluated several times a day to assess heart rate and activity level. This is particularly true when determining if fetal distress is significant enough to prompt intervention such as induction of parturition. Induced parturition is rarely considered in mares with placentitis. More often, measures are instituted to encourage pregnancy maintenance with the goal of allowing sufficient fetal maturation to occur before delivery. Fig. 6. This placenta was affected by nocardia-form placentitis. Note the characteristic mucoid exudate located at the base of the Treatment Options pregnant uterine horn. Twin Pregnancies Twin pregnancies are best managed by early detection (day 13–15 gestation) and elimination of one thorax, which is the end that narrows into the embryonic vesicle using the manual crush tech- cervical spine. The average heart rate in a fetus nique. Mares carrying twins late in gestation are Ͼ300 days gestation is 75 Ϯ 7 bpm.4 Fetal heart at a significant risk. Although some mares may rate slows by ϳ10 bpm at Ͼ330 days gestation, but successfully deliver live twins, the majority of mares it can vary with activity levels. Heart rates can will lose one or both pregnancies in the latter one- increase by 15–20 bpm during periods of activi- third of gestation.12 Those mares that abort late in ty.7,8 Consistently low or high fetal heart rates gestation (Ͼ250 days) or deliver twins at term are at are associated with fetal stress. Fetuses experi- increased risk for dystocia. encing distress often become bradycardic initially Management of late-gestation twins (Ͼ8 mo) and then tachycardic in the terminal phase of would include the following approaches: (1) termi- life.8,9 nate the pregnancies, or (2) allow the pregnancies to Confirmation of twins is generally made by iden- continue, monitor the mare, and provide assistance tifying two fetal thoraces and/or beating hearts. during delivery, if possible. Neither of these op- Measurements of fetal thoraces can be used to con- tions is particularly palatable to the practitioner. firm the presence of twins if thoracic size differs Advising an owner on the approach that is best between fetuses. Additionally, the orientation of depends on the status of the fetuses (live or dead), the thorax can be used to verify the presence of twin size of the fetuses, value of the fetuses relative to the fetuses. mare, and economics. Fetal activity level and tone are easily determined Size of the fetus is important relative to the sur- when examining a fetus for heart rate. Fetal activ- vival of the fetuses. If one fetus is significantly ity can vary during the examination period, because larger than the other fetus, it is likely that the larger fetuses have periods of sleep and wakefulness. fetus will also have a better placental interface with In response to the ultrasound beam, the normal the endometrium. In this scenario, the smaller fe- fetus commonly becomes very active during the ex- tus often dies in the middle of pregnancy and is amination period. Fetal activity has been de- maintained as a sterile mummy. The smaller fetus scribed on a 0–3 scale.4,7 A grade of 0 indicates no poses a lesser threat for dystocia during delivery, fetal movement over a minimum examination period and the larger fetus may stand a reasonable chance of 30 min. A grade of 1 is assigned if minimal for survival. However, if both fetuses are similar in movement occurs (Յ33% of examination time), 2 if size and both are alive, mortality rates are increased moderate activity is noted (33–66% of examination at several junctures. Often, these fetuses are de- time), and 3 if the fetus is very active during the livered prematurely because of inadequate placental examination (Ն66% of the time). Fetal “tone” is a support. When same-sized twins are delivered subjective term describing the viability of the fetus. close to term, they are often small and unthrifty. A live fetus has excellent “tone” in that it is active; it Mortality rates for live-delivered twin foals are sig- also flexes and extends the torso, neck, and limbs.4,7 nificant (50%).12 Furthermore, same-sized twins A fetus without “tone” is most frequently dead or in pose the greatest risk for dystocia. Thus, not only the terminal stage of life. An atonic fetus is flaccid, are the fetuses in jeopardy, but the mare is as well. lies passively within the uterus, and may be folded An owner wishing to allow a mare to carry same- in on itself. Clearly identifying the atonic fetus can sized twins to delivery should be advised of the risks

AAEP PROCEEDINGS ր Vol. 53 ր 2007 297 IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE to the mare and fetuses. In addition, this mare will 24 h, PO) was added to the trimethoprim sulfa and require vigilant observation and an attended foal- pentoxifylline protocol. Ten of twelve mares with ing, if possible. experimentally induced placentitis delivered live With either continuation or termination of twin foals after treatment with the protocol. The com- pregnancies, an owner would be advised to hospital- bined effects of the drugs may have provided the ize the mare so that delivery could be monitored. necessary intervention for pre-term delivery by ad- If the pregnancy were terminated electively, the pe- dressing microbial infection, inflammation, and riod of hospitalization would range from ϳ 2to5 uterine contractility. Also, early diagnosis of dis- days with an uncomplicated delivery. Factors that ease and initiation of treatment probably contrib- would influence hospitalization duration might in- uted to the positive outcome in this study. clude ease of delivery, trauma to the uterus or caudal birth canal, dystocia, and retained fetal 3. The “Colicky” Late-Pregnant Mare membranes. The late-pregnant mare suffering from acute pain is Placentitis a diagnostic challenge for the equine practitioner. Placentitis in mares is commonly caused by bacteria The first challenge is to accurately differentiate dis- ascending through the vagina.11,13,14 The most fre- ease from end-stage gestation and labor. Mares quent bacterial pathogens implicated in equine pla- having gastrointestinal distress can behave simi- centitis are Streptococcus equi subspecies larly to mares in the early stages of labor. Some- zooepidemicus, Escherichia coli, Klebsiella pneumo- times, these conditions overlap. The second nia, and Pseudomonas aeruginosa.15 Although challenge is to treat the disease and save the life of bacterial infection initiates disease, recent work the mare and the fetus. Colic, and conditions such from an experimental model of ascending placentitis as endotoxemia and laminitis that occur second- in pony mares showed that premature delivery may arily, pose significant threats to the mare and fe- occur secondary to inflammation of the chorion tus.23 Systemic compromise occurs in the face of an rather than as a consequence of fetal infection.16,17 endotoxic insult; this results in the release of endog- These inflammatory processes result in prostaglan- enous cytokines such as tumor necrosis factor alpha, din production (prostaglandin E2 and prostaglandin interleukins, and prostaglandins.24 Cytokines F2 ␣) and stimulation of myometrial contractility, have profound effects on the systemic health of the which results in pre-term delivery.18,19 Therefore, mare and affect the circulation and metabolism of therapies directed at resolving microbial invasion, the placenta.24,25 inflammation, and uterine contractions are probably needed to effectively combat placental infections. History and Physical Examination Several recent studies have helped piece together the puzzle of therapeutic usefulness in mares with What Is the Gestational Length of the Mare, and placentitis. Two studies from the University of How Long and to What Degree Has the Mare Florida20,21 employed in vivo microdialysis to deter- Exhibited Symptoms of Pain? mine if selected drugs attained therapeutic concen- Mares late in gestation often suffer mild to interme- trations in allantoic fluid of normal pony mares and diate levels of discomfort because of the large size of mares with experimentally induced placentitis. the fetus and the pressure on the abdominal contents. a Penicillin potassium G (22,000 U/kg,q6h,IV), Their pain is generally intermittent. Mares pre- b gentamicin sulfate (6.6 mg/kg, q 24 h, IV), tri- senting with severe or unrelenting pain late in c methoprim sulfamethoxazole (30 mg/kg, q 12 h, gestation usually have a gastrointestinal lesion. d PO), and pentoxifylline (8.5 mg/kg, q 12 h, PO) were Common lesions seen in pregnant mares include all detected in allantoic fluid of both normal and large-colon displacement and torsions, large-colon infected pony mares. Furthermore, concentrations impactions, and small-intestinal lesions.23,26,27 of antimicrobials in allantoic fluid were sufficient to Recurring pain in the late-pregnant mare that is ϳ show a short-term ( 4 h) effect. Both penicillin unrelated to the gastrointestinal system is usually and trimethoprim sulfamethoxazole had effective from uterine torsion. Uterine torsion is rela- minimum inhibitory concentrations (MIC) against tively rare; however, it is necessary to rule out S. equi ssp. zooepidemicus. Gentamicin concentra- uterine torsion in painful mares in the last trimes- tions in allantoic fluid were adequate to be effective ter of gestation. against Escherichia coli or Klebsiella pneumoniae. In a subsequent study,22 trimethoprim sulfamethox- Does the Mare Have a History of Colic? azole and pentoxifylline were identified in fetal and placental tissues obtained from mares with experi- Although not a fail safe for diagnosis, it is helpful to mentally induced placentitis. Treating infected know the mare’s past medical history. A mare that mares with these two drugs prolonged gestation but has experienced several episodes of colic in her past, did not result in more live-born foals. Recent work particularly when not pregnant, may have a greater from the University of Floridae showed encouraging likelihood of having gastrointestinal disease than results when altrenogestf (Regumate, 0.088 mg/kg, q idiopathic colic related to pregnancy.

298 2007 ր Vol. 53 ր AAEP PROCEEDINGS IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE Has the Mare Responded to Analgesics? a gastrointestinal lesion can show several clinical Gastrointestinal conditions causing colic in late- signs, but they are often dehydrated and leukopenic (neurtropenic with a left shift and toxicity) with ele- pregnant mares often result in unrelenting pain 30,31 that is refractory to the administration of analge- vated blood-lactate levels. sics. Colon torsions cause violent pain in the mare. Treatment Pregnant mares with idiopathic, low-grade colic are more likely to experience relief from analgesic ad- Medical Support ministration. Uterine torsion generally results in mild to moderate discomfort (depending on the de- Identification of the source of pain in a late-pregnant gree of the torsion) that is not relieved with mare is paramount to executing proper therapy. analgesics. Differentiating between pain from a gastrointestinal lesion and discomfort associated with pregnancy is a Transrectal Palpation of Abdominal Contents critical first step. In some instances, distinguish- ing an abnormality can be difficult. Treatment Transrectal palpation of the abdominal contents can should be directed at providing systemic support for be limited in the late-pregnant mare. The gravid the mare and limiting hypoxia to the foal. Cardio- uterus and fetus occupy the majority of the palpable vascular support is provided with IV fluid therapy. abdomen. Assessment for gross abnormalities in Antimicrobial coverage is important in mares with the gastrointestinal tract, such as distended small endotoxemia, enteritis, or any other bacterial dis- intestine or impacted bowel, may be possible despite ease. Anti-inflammatory therapy is necessary to the enlarged uterus. Transrectal evaluation of the counteract the inflammatory cascade that ensues reproductive tract is the most accurate method for with gastrointestinal disease. Progestin therapy diagnosing uterine torsion in the mare. Depending (altrenogest, Regumate, at double dose of 0.088 mg/ on the direction of the torsion, the broad ligament on kg, q 24 h, PO) may be useful for counteracting the side of the torsion is often more caudal and is uterine contractility. palpable as a tight vertical band.28 The opposite ligament courses horizontally over the top of the Surgical Disease uterus and is then displaced ventrally. Some of the most common causes of colic in the Transabdominal Ultrasonography late-pregnant mare (large-colon abnormalities and small-intestinal lesions) necessitate surgical inter- The gravid uterus generally obscures routine exam- vention. Surgery, in itself, poses a risk to the fetus. ination of the abdominal contents using ultrasonog- Fetuses suffering from intra-operative hypoxia in raphy. However, it is a useful tool for localizing the last 60 days of gestation showed higher mortal- specific abnormalities such as distended small intes- ity in one study.23 The gravid uterus places pres- tine, thickened intestinal wall, and free fluid in the sure on the diaphragm when the mare is in dorsal abdomen. Areas of the large colon can be assessed. recumbency, which reduces oxygenation to the mare Fluid pockets in the ventral abdomen can be identi- and fetus. However, one cannot underestimate the fied for abdominocentesis. Fetal assessment, as de- importance of correcting the initial cause of disease scribed earlier, can be performed. in the mare. The benefits of surgical correction of a life-threatening condition generally outweigh the Abdominocentesis risks of intra-operative hypoxia. Changes in abdominal fluid are used frequently as a The question about performing an elective Cesar- marker for gastrointestinal disease. As with other ean section at the time of laparotomy frequently procedures, the uterus can limit the usefulness of arises in pregnant mares undergoing colic surgery. this tool in the pregnant animal. Often, the uterus Occasionally, the mare or fetus might benefit from in the late-term mare lies in the ventral abdomen, Cesarean section and removal of the fetus. Most which eliminates pockets of peritoneal flu- often, this is not a wise choice. One must weigh the id. Transabdominal ultrasonography can aid in de- consequences to the mare if the fetus is left in place tecting a pocket of fluid to sample. If a sample is against the consequences to the foal if it is removed obtained, peritoneal fluid character is similar between prematurely. In most cases, the odds favor correct- 29 normal pregnant and non-pregnant animals. Cell ing the gastrointestinal insult and leaving the fetus counts and protein levels are increased with compro- in utero until the mare delivers it herself. The mised bowel or uterus. Gross visual character of the equine fetus is unique in that final maturational fluid can also be assessed. changes in essential body systems such as the lungs occur in the last week of gestation.32 Unless the Laboratory Values fetus is mature at the time of surgery, the prognosis Laboratory values for complete blood count (CBC), se- for survival of the neonate is poor. Frequently, cli- rum chemistry, and blood gas should all be within ents will report that the mare is “due” based on normal limits for a late-gestational mare. Derange- gestational length (typically around 335–345 days ments in values can be seen with different causes of gestation).33 However, gestational length is highly colic. Mares experiencing endotoxemia secondary to variable in the mare. Therefore, gestational length

AAEP PROCEEDINGS ր Vol. 53 ր 2007 299 IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE is not a good parameter when deciding to induce parturition or perform a Cesarean section. Mam- mary-gland development and presence of colostral secretions are more accurate indicators of fetal readiness for extra-uterine life.34 Mammary-gland secretions can be monitored using commercial serum- chemistry analyzers (after dilution) or stall-side tests. The advantage of laboratory analysis of secretions is that quantitative figures for calcium, sodium, and potassium can be obtained. Values of at least 40 mg/dl of calcium and inversion of sodium (decreases) and potassium (increases) are indicative of a mature foal.34 Inversion of the sodium and potassium often occurs around 30 mEq. Disadvantages for using a laboratory to analyze mammary secretions are turn-around time and expense. Stall-side tests are also available to monitor mammary-secretion electrolytes.g,h These tests are semiquantitative and measure calcium and Fig. 7. This mare was diagnosed with hydrops amnii. A sup- magnesium but not sodium or potassium. Based on portive abdominal bandage is pictured here. calcium concentrations in secretions, a prediction is made regarding impending parturition in the mare. Using one of these tests, one can predict fetal matu- 35 rity, which can be used to support or discourage a licus to the ground may all increase over time. decision to surgically remove a fetus. One must keep Ventral abdominal edema is common with this con- in mind that this is not a perfect system, and inherent dition and should be distinguished from actual ab- risks exist when dictating delivery time of a foal. dominal enlargement (Fig. 7). A general concern for a pregnant mare with a In contrast, mares experiencing a complete rupture healing abdominal incision is that she will eviscer- of the pre-pubic tendon will show a rapid change in ate through the incision during parturition. Anec- abdominal stature as well as posture. This condition dotally, evisceration during parturition is rare. occurs in aged mares, draft breeds, and mares suffer- Although labor is an explosive event, mares are pro- ing from hydropic conditions. Most notably, the mare tective of themselves. Mares with abdominal inci- will adopt a “sawhorse” stance with a distinctive cra- sions are more likely to have a poor abdominal press nial tilt to her pelvis. A significant plaque of ventral because of pain associated with the healing incision. edema is often noted in this condition. The mare with Monitoring the mare during delivery to assist with a complete rupture will also lose definition in her flank parturition or a crisis is warranted. region. Finally, the mammary gland of the mare with a ruptured pre-pubic tendon is distinguished 4. The Mare With Acute Abdominal Enlargement from other conditions in that there is massive edema to the gland and hemorrhagic discharge expressed A late-pregnant mare that develops unusual abdominal from the teats; additionally, the mare has a cranial distention is frequently in great jeopardy herself, and she orientation (Fig. 8). The mare with a ruptured pre- is also at risk of losing her pregnancy. Causes of aberrant abdominal distention include hydropic conditions (hydrallantois and hydramnios), rupture of the pre-pubic tendon, and abdominal-wall herniation. One or more of these conditions may contribute to acute abdominal enlargement. Although these cases occur infrequently, they are life threatening. Prompt diagnosis and correction of the condition may improve the mortality of the mare and/or foal.

History and Physical Examination When Did Abdominal Distention Become Apparent in the Mare, and How Quickly Did It Progress? Mares experiencing hydropic conditions typically show abdominal distention over a period of 2–14 days in mid to late gestation. Distention usually occurs somewhat rapidly but insidiously, and it may not be recognized early on in the process. Abdomi- Fig. 8. Hemorrhagic secretions obtained from the teats of a nal circumference, distance from the mammary mare with rupture of the pre-pubic tendon. (Photo courtesy of gland to the umbilicus, and distance from the umbi- Dr. Claire Card, University of Saskatchewan.)

300 2007 ր Vol. 53 ր AAEP PROCEEDINGS IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE pubic tendon is reluctant to move and may prefer to be conditions are characterized by an abnormally large, recumbent. Mares having a partial rupture of the fluid-filled uterus in which a fetus is not easily bal- tendon may have less distinctive clinical signs than loted. The fetal fluids may be more cellular than those noted in the mare with a complete tendon rup- seen in a normal pregnancy. Defects in the body ture. Mares with a partial rupture show perceived wall or pre-pubic tendon are not easily distinguished abdominal enlargement because of a loss of tendinous using transrectal palpation and ultrasonography be- attachment to the pubis. The mare with a partial cause of interference from the fetus and pregnant tendon rupture will not have a distinct “sawhorse” uterus. stance. Differentiating a partial tendon rupture from other conditions, such as abdominal-wall hernia or Transabdominal Ultrasonography hydrops, can be challenging, because the signs are Transabdominal examination of the abdominal mus- significantly less distinctive. Either complete or par- culature and contents is very useful when distin- tial rupture of the pre-pubic tendon can occur second- guishing between conditions contributing to arily to hydropic conditions. abdominal enlargement in the pregnant mare. The mare with an abdominal-wall hernia or rent Hydropic conditions will be characterized by an ab- will have the most variable time frame for abdomi- normally large volume of fetal fluids. Transab- nal enlargement. This condition can be a result of dominal ultrasonography can be used to distinguish trauma to the abdominal musculature; in that case, which placental compartment is enlarged (amnion abdominal enlargement is likely to be rapid. Fur- versus allantois), which can help in diagnosis. Fur- thermore, traumatically induced rents are usually thermore, using transabdominal ultrasound guid- unilateral (Fig. 9). If abdominal-wall herniation ance, fluid samples can be obtained from the amnion results secondarily to vascular occlusion of the cau- and/or chorioallantois and analyzed for chemical dal epigastric and caudal superficial veins, the de- properties that can definitively identify the enlarged fect may result from separation of the musculature; compartment.35,36 Serial measurements can be this may occur less rapidly. made of the placental compartments in specific quadrants to monitor increases or decreases in fluid What Is the Mare’s Attitude and Systemic volume over time.7 Health Status? Ultrasonographic examination of the abdominal- With all causes of abdominal enlargement, the mare wall area can be useful when making a diagnosis. is likely to be depressed, inappetant, and reluctant Ultrasonographic examination of a body-wall defect to move. Heart rate and respiratory rate may be will reveal muscular disruption and edema. Iden- elevated because of abdominal-fluid pressure on the tification of ingesta-filled intestines within a defect diaphragm in hydropic conditions or pain in any of is diagnostic for a hernia. The extent of damage in the conditions. CBCs and serum-chemistry values these cases may not be determined until after should be unchanged with these conditions. foaling.

Transrectal Palpation and Ultrasonography Treatment Options Transrectal palpation and ultrasonography is most Treatment choices for all of these conditions are useful for diagnosing hydropic conditions. These contingent on several factors: (1) overall status of the mare (severity of condition, systemic health, and pain), (2) prognosis for recovery and viability of the mare and/or foal, and (3) client priority for surviv- ability of the mare and/or foal. First, the overall condition of the mare should be considered. If the mare is reasonably comfortable and the lesion is manageable, one might consider supportive care in an effort to save both the mare and foal. If the mare is in unrelenting pain and the condition is clearly compromising her quality of life, one might choose to sacriﬁce either the mare or foal, depending on the wishes of the client. Fetal maturity is an important part of the equation. Performing a terminal Cesarean section on a mare at Ͻ300 days gestation is unlikely to result in a viable neonate. Determining the best course of treatment to maxi- mize a positive outcome for all involved is a challenging goal. Abdominal Support Fig. 9. This mare suffered a unilateral abdominal-wall rupture Abdominal support can be provided in mares with and herniation. any of these conditions. Support is provided to im-

AAEP PROCEEDINGS ր Vol. 53 ր 2007 301 IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE prove the comfort of the mare. Additionally, mares that have not suffered full rupture of the pre-pubic tendon may have reduced risk of further tendon damage if the abdomen is supported. Several options for abdominal support are available. The mare’s abdomen can be wrapped with several rolls of 4-in elasticized bandage material (i.e., Elastikoni). The bandage material is applied in an overlapping fashion from behind the withers to the flank region. Care should be taken to avoid applying a constrict- ing bandage. Rolls of elastic bandage material can be unrolled, rerolled loosely, and then wrapped tautly but not tightly around the abdomen. This type of bandage should be removed at least every other day to verify that bandage sores or ischemic necrosis is not occurring. Estimated cost for this type of bandage is ϳ$90–100/day. A less expensive alternative is to use porous, 2-in white tape to make Fig. 10. A commercially available abdominal wrap, secured with a belly bandage.j This method reportedly provides several strips of Velcro, supports the abdomen of this mare with a taut girdle without over restricting, and it removes an abdominal-wall rent. less hair from the skin. Alternatively, several sources exist for commercially available belly bandages. These bandages typically are made from a piece of canvas or stretchy Given the considerable risk to the mare with hy- fabric with Velcro bandages to secure the bandage in dropic conditions (possible pre-pubic tendon rup- place and provide different levels of support (Fig. ture, muscular tear, or hypovolemic shock during 10). Commercially available products offer the ad- parturition), induced parturition has been advocat- vantages of one-time only expense ($350–400) and ed.28 A recent report35 described management of a reusability of the product. The bandages are also mare with hydrops amnion that resulted in delivery readily washed after they become soiled. With a of a live foal. The mare was diagnosed with hy- reusable bandage, the wrap can be taken off for a dramnios at 265 days gestation. The fetus was vi- period of time each day to allow for monitoring of the able. The mare was managed using stall skin under the wrap as well as to allow air to circu- confinement, a supportive abdominal wrap, altreno- late to the area. Although the bandages are gener- gest and flunixin meglumine, and daily foal moni- ally comfortable, a horse will occasionally resent the toring until 321 days gestation at which time she wrap and become reluctant to move or eat. Remov- spontaneously went into labor. The mare suffered ing the wrap each day allows the animal an oppor- hypovolemic shock in the immediate post-partum tunity to “rest” from the bandage. Examples of period, and hypertonic and isotonic IV fluids were commercially produced bandages that have provided administered. Both the mare and foal survived. good results for abdominal defects in mares include Although this study only reports the outcome of one the CM Heal Hernia Belt and Post-Surgical Pres- clinical case, the resultant viable mare and foal call sure Bandage produced by CM Equine Productsk into question the unequivocal induction of parturi- and the Boa by Rewrap.l Both of these bandages tion in cases of hydrops. Certainly, in the case of a provide good abdominal support through the use of non-viable foal or a mare whose life is in jeopardy, Velcro bands. Furthermore, they are available in a induced parturition would be a better treatment variety of sizes that is important when fitting a choice. Mares with hydropic conditions that are bandage to a mare. Although the expense of these allowed to proceed with pregnancy should be moni- bandages is considerable, it can be minimal com- tored constantly to determine changes in abdominal pared with the price of a mare or foal. diameter, identify defects in the abdominal wall musculature or pre-pubic tendon, and determine vi- Induced Parturition ability of the fetus. The decision to induce parturition in mares with Mares with abdominal-wall hernias or muscular abdominal defects or hydropic conditions is not as rents are best served with external-support wraps, clear cut as was once thought. The primary advan- serial monitoring of mammary-gland secretions, and tage for inducing parturition in mares with these induced parturition. Mares with these conditions conditions is controlling time of delivery to provide are at high risk for having a poor or non-existent assistance. However, induced parturition in- abdominal press during parturition. Furthermore, creases the risks for premature delivery and dysto- these mares are at risk for evisceration of abdominal cia. Blanchard et al.37 suggested that in the case of contents through the abdominal wall depending on hydropic conditions, the fetus was often non-viable the severity of the lesion. Therefore, mammary- or had limited likelihood of surviving after delivery. gland secretions should be carefully monitored for

302 2007 ր Vol. 53 ր AAEP PROCEEDINGS IN-DEPTH: PERINATOLOGY—END OF PREGNANCY THROUGH BEGINNING OF LIFE changes that could indicate imminent parturition 3. Renaudin CD, Liu IKM, Troedsson MHT, et al. Transrectal (calcium Ͼ40 mg/dl and inversion of sodium and ultrasonographic diagnosis of ascending placentitis in the mare: a report of two cases. Equine Vet Edu 1999;11:69–74. potassium); then, parturition can be attended. 4. Reef VB, Vaala WE, Worth LT, et al. Ultrasonographic as- Induced parturition is useful to ensure that person- sessment of fetal well-being during late gestation: develop- nel are available to assist with delivery. Foals de- ment of an equine biophysical profile. Equine Vet J 1996;28: livered from mares having any of the conditions 200–208. described in this paper are at a high risk for hypoxia 5. Adams-Brendemuehl C, Pipers FS. Antepartum evaluation of the equine fetus. J Reprod Fertil 1987;35:565–573. during delivery. In turn, induced parturition can 6. Vaala WE, Sertich PL. Management strategies for mares at 38 contribute to intrapartum hypoxia. One must risk for periparturient complications. Vet Clin North Am weigh the benefits of assisted delivery and prompt [Equine Pract] 1994;10:237–265. medical attention for the mare and foal versus the 7. Reef VB, Vaala WE, Worth LT, et al. Ultrasonographic eval- risks inherent to induced parturition. uation of the fetus and intrauterine environment in healthy mares during late gestation. Vet Radiol Ultrasound 1995; A ruptured pre-pubic tendon causes several of the 36:533–541. same problems that are experienced with hydropic 8. Pipers FS, Adamsbrendemuehl CS. Techniques and appli- conditions or abdominal-wall defects. The severity cations of trans-abdominal ultrasonography in the pregnant of the rupture often drives therapy decisions for the mare. J Am Vet Med Assoc 1984;185:766–771. 9. Pipers FS, Zent W, Holder R, et al. Ultrasonography as an mare. If a mare has a completely ruptured tendon, adjunct to pregnancy assessments in the mare. JAmVet it is unlikely that she will survive beyond the birth Med Assoc 1984;184:328–334. of the foal. In that case, providing support for the 10. Reef VB, Sertich PL, Turner RMO. Equine diagnostic ultra- mare as long as possible to allow the fetus to mature sound. Philadelphia: W.B. Saunders Co, 1998. is a priority. As with abdominal-wall hernias, the 11. Hong CB, Donahue JM, Giles RC, et al. Etiology and pa- thology of equine placentitis. J Vet Diag Invest 1993;5:56– pregnancy should be monitored, and parturition 63. should be attended if at all possible. Induced par- 12. Jeffcott LB, Whitwell KE. Twinning as a cause of fetal and turition or elective Cesarean section may be the best neonatal loss in Thoroughbred mares. J Comp Pathol 1973; choice for mares with terminal conditions. 83:91–106. 13. Platt H. Infection of the horse fetus. J Reprod Fertil 1975; Elective Cesarean Section 23(Suppl):605–610. 14. Whitwell K. Equine infectious diseases V. Lexington, KY: Elective Cesarean section is an option for mares that University of Kentucky Press, 1988. have conditions related to acute abdominal enlarge- 15. Acland HM. Abortion. In: McKinnon AO, Voss JL, eds. ment. Advantages to this procedure versus in- Equine reproduction. Philadelphia, PA: Lea & Febiger, 1993;554–562. duced parturition include a controlled time of 16. Leblanc MM, Giguere S, Brauer K, et al. Premature deliv- delivery and a reduced role for the mare in active ery in ascending placentitis is associated with increased ex- delivery. Disadvantages of Cesarean section in- pression of placental cytokines and allantoic fluid clude premature delivery of the foal and complica- prostaglandins E-2 and F-2 alpha. Theriogenology 2002;58: 841–844. tions from general anesthesia and/or abdominal 17. Mays MBC, LeBlanc MM, Paccamonti D. Route of fetal surgery. Elective Cesarean section is best per- infection in a model of ascending placentitis. Theriogenol- formed in mares that have had changes in mamma- ogy 2002;58:791–792. ry-secretion electrolytes indicative of adequate fetal 18. Pollard JK, Mitchell MD. Intrauterine infection and the maturity. In some cases, Cesarean section is per- effects of inflammatory mediators on prostaglandin production by myometrial cells from pregnant women. Am J Obstet formed as a terminal procedure. This most often Gynecol 1996;174:682–686. occurs when the condition of the mare is considered 19. Dudley DJ, Trautman MS. Infection, inflammation, and irreversible and inhumane as well as life threaten- contractions—the role of cytokines in the pathophysiology of ing to the fetus. The timing of a terminal Cesarean preterm labor. Semin Reprod Endocrinol 1994;12:263–272. section is rarely in concert with fetal maturity in 20. Murchie TA, Macpherson ML, LeBlanc MM, et al. Continuous monitoring of penicillin G and gentamicin in allantoic fluid of these cases. Consequently, neonatal morbidity is pregnant pony mares by in vivo microdialysis. Equine Vet J often high. 2006;38:520–525. In summary, conditions affecting the late-preg- 21. Rebello SA, Macpherson ML, Murchie TA, et al. Placental nant mare are challenging to both diagnose and transfer of trimethoprim sulfamethoxazole and pentoxifylline in pony mares. Anim Reprod Sci 2006;94:432–433. treat. One must consider both the life of the mare 22. Graczyk J, Macpherson ML, Pozor MA, et al. Treatment and fetus when making treatment decisions. Fur- efficacy of trimethoprim sulfamethoxazole and pentoxifylline thermore, the consequences of those actions must be in equine placentitis. Anim Reprod Sci 2006;94:434–435. considered in the face of the animal’s future 23. Santschi EM, Slone DE, Gronwall R, et al. Types of colic livelihood. and frequency of postcolic abortion in pregnant mares—105 cases (1984–1988). J Am Vet Med Assoc 1991;199:374–377. 24. Moore JN. Milne lecture: gastrointestinal disease, in Pro- References and Footnotes ceedings. Am Assoc Equine Pract 2001;49:53–74. 1. Renaudin CD, Troedsson MHT, Gillis CL. Transrectal ultra- 25. Santschi EM, Slone DE. Maternal conditions that cause sonographic evaluation of the normal equine placenta. Equine high-risk pregnancy in mares. Compend Cont Educ Pract Vet Edu 1999;11:75–76. Vet 1994;16:1481–1487. 2. Renaudin CD, Troedsson MHT, Gillis CL, et al. Ultrasono- 26. Steel CM, Gibson KT. Colic in the pregnant and peripartu- graphic evaluation of the equine placenta by transrectal and rient mare. Equine Vet Edu 2001;13:94–104. transabdominal approach in the normal pregnant mare. The- 27. Boening KJ, Leendertse IP. Review of 115 cases of colic in riogenology 1997;47:U5. the pregnant mare. Equine Vet J 1993;25:518–521.

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28. Frazer GS, Embertson R, Perkins NR. Complications of late 36. Paccamonti D, Swiderski C, Marx B, et al. Electrolytes and gestation in the mare. Equine Vet Edu 1997;9:306–311. biochemical enzymes in amniotic and allantoic fluid of the 29. Frazer GS. Interpretation of peritoneal fluid changes in pe- equine fetus during late gestation. Biol Reprod Mono 1995; ripartum mares. In: Robinson NE, ed. Current therapy in 1:39–48. equine medicine. Philadelphia, PA: W.B. Saunders Co., 37. Blanchard TL, Varner DD, Schumacher J, et al. Manual of 2003;294–297. equine reproduction. St. Louis, MO: Mosby, 2003. 30. Franklin RP, Peloso JG. Review of the clinical use of lactate, in 38. Macpherson ML, Chaffin MK, Carroll GL, et al. Three Proceedings. Am Assoc Equine Pract 2006;52:305–309. methods of oxytocin-induced parturition and their effects of 31. Barton MH. Endotoxemia. In: Robinson NE, ed. Current foals. J Am Vet Med Assoc 1997;210:799–803. therapy in equine medicine. Philadelphia, PA: W.B. Saun- ders Co., 2003;104–108. 32. Silver M, Ousey JC, Dudan FE, et al. Studies on equine aPfizer Animal Health, Exton, PA 19341. prematurity. 2. Post natal adrenocortical activity in rela- b tion to plasma adrenocorticotropic hormone and catechol- Gentocin, Schering-Plough, Union, NJ 07083. cLannett Co., Inc., Philadelphia, PA 19136. amine levels in term and premature foals. Equine Vet J d 1984;16:278–286. Apotex Corp., Toronto, Ontario, Canada M9L 1T9. e 33. Rossdale PD, Ricketts SW. Equine stud farm medicine. Bailey CS. Personal communication. September 2006. f Philadelphia: Lea & Febiger, 1980. Regumate, Intervet Inc., Millsboro, DE 19966. g 34. Ousey JC, Dudan F, Rossdale PD. Preliminary studies of Predict-A-Foal, Animal Health Care, Williston, VT 05495. mammary secretions in the mare to assess fetal readiness for hFoalWatch, Chemetrics, Calverton, VA 20138. birth. Equine Vet J 1984;16:259–263. iJohnson and Johnson, New Brunswick, NJ 08901. 35. Christensen BW, Troedsson MHT, Murchie TA, et al. Man- jMorton A. Personal communication. March 2007. agement of hydrops amnion in a mare resulting in birth of a kCM Equine Products, Norco, CA 92860. live foal. J Am Vet Med Assoc 2006;228:1228–1233. lBoa, Re-wrap Pro Veterinary Products, Paris, KY 40361.

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