IN-DEPTH: CONDITIONS AND MANAGEMENT OF THE PERIPARTUM MARE


with either a body wall hernia only or both a prepu- bic tendon rupture and a body wall hernia. They found no difference in prognosis based on the type of condition and had better results in mares managed conservatively than those that had intervention by either induction of parturition or Caesarean. Con- servative management involved support for the mare and frequent monitoring of fetal wellbeing. The mare’s management comprised of abdominal support, as described previously for mares with hy- drops, using commercial belly bandages or wraps, analgesia provided by nonsteroidal anti-inflamma- tory drugs and stable or stall rest (with careful hand walking to reduce ventral edema). Somemares can become very painful and may need additional pain relief from drugs such as intravenous lidocaine con- tinuous infusion or butorphanol injection (0.01–0.04 mg/kg, IV this drug has a fairly immediate effect and to maintain analgesia requires injecting every 3 hours). If the mare’s condition can be stabilized, then the pregnancy can continue to progress to- wards full term allowing the fetus to reach full ma- turity without the need for intervention. Serial ultrasound monitoring to detect any worsening of a partial prepubic tendon rupture or the size and ex- tent of abdominal muscle ruptures is useful in de- termining the course of action and the prognosis. Frequent fetal monitoring to determine fetal wellbe- ing is important, with regular ultrasound examina- tions, to determine fetal biophysical parameters and detect any deterioration in fetal health that might lead to the need for sudden intervention. Monitoring the change in maternal serum proges-


terone (and progestagens) concentrations and mam- mary secretion electrolyte values can help confirm the fetus is starting to reach a state of readiness for birth similarly, ensuring that the mare has a fully attended delivery and any assistance necessary is immediately available is crucial to a good outcome. In the review of cases reported by Ross and co- authors, 7 of 8mares allowed to foal naturally did so without any significant assistance.23 These find- ings were in contrast to the often held view that induction of parturition or Caesarean section is a necessity for mares with prepubic tendon conditions. Monitoring for evidence of fetal readiness for birth is particularly helpful in these cases as decisions about the need for intervention, should the mare’s condi- tion suddenly deteriorate, can be balanced with a risk assessment of whether the fetus is sufficiently mature and ready for birth. The foal requires an active hypothalamo-pituitary-adrenal (HPA) axis for final organ maturation and to ensure postnatal survival. Generally speaking, the aim is to always try and maintain the pregnancy beyond 300 days of gestation; few foals will survive if born prior to this. Nonetheless, even if this milestone is reached, the likelihood of a sufficient level of maturity for sur- vival is not guaranteed. In some cases, stimulating early fetal maturation may be wise if the situation in the mare deteriorates


or the fetoplacental environment deteriorates to such an extent that the foal has a better chance of survival if delivered. Researchers have investi- gated the use of dexamethasone to promote fetal maturity. In one recent study, healthy Thorough- bred mares were treated for 3 days with 100 mg intramuscular dexamethasone from day 315–317 of gestation. Mares were allowed to deliver foals nat- urally. The length of pregnancy was shortened in treated mares, on average, by nearly 2 weeks com- pared with normal, foaling mares. The time be- tween the last administration of dexamethasone and foaling ranged from 1 to 8 days in the treated mares. Maternal serum progestagens rose significantly dur- ing the 3 days of treatment, indicating a response consistent with activation of the fetal HPA axis. Although, there was evidence of suppression of fetal adrenocortical activity, all the foals were healthy at birth. Foals from treated mares were significantly smaller than foals from normal, foaling mares. None of the treated mares suffered any untoward sequelae, such as laminitis, although all mares had poor udder development and did not produce normal colostrum.24 There is a concern that in systemi- cally ill mares who may already have raised cortisol and progestagen levels, and are therefore possibly already stimulating activation of the fetal HPA axis, that any maternal treatment with dexamethasone may disrupt HPA axis induced fetal maturation. This might lead to a disturbance in the final mat- uration of vital organ systems with the conse- quence that the fetus is ill-prepared for postnatal life. Despite these concerns, and albeit in a small number of clinical cases, high-dose dexametha- sone treatment has been considered advantageous for salvaging pregnancies in selected cases. Antic- ipating that about 5 days will be needed on average for the treatment to be effective must be borne in mind if electing to use this regime. Evidence of suspected activation of the fetal HPA axis can be determined by checking for elevated serum proge- stagens and full-term milk electrolyte profiles in the mare prior to treatment. Ideally, the results will indicate there is no evidence of fetal maturation. If the results indicate significant HPA axis activity may already be occurring, the negative effects of dexamethasone treatment should be factored in as this may significantly worsen the fetal outcome. If possible, allowing the mare to foal spontaneously will give her foal the best opportunity to have reached a level of readiness for birth that results in it being sufficiently mature to be able to survive postnatally. However, if circumstances dictate that urgent induction of foaling or a Caesarean is indicated, this is normally when the mare is in an imminently terminal state, the likely degree of ma- turity of the foal can also be anticipated by monitor- ing the change in maternal serum progestagen and milk electrolyte profile following treatment.


AAEP PROCEEDINGS  Vol. 65  2019 153


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