Neonatal monitoring after full-term birth induction in a Thoroughbred mare - case reportABSTRACT
Mares have a variable gestation length, and labor induction is reserved for high-risk pregnancies due to the unpredictability of fetal maturity. This case reports an induced parturition in a Thoroughbred mare with acute laminitis at 327 days of gestation. Labor was achieved with intravenous oxytocin, resulting in eutocic delivery. However, the foal presented with signs of severe immaturity-absent suckling reflex, inability to rise, flexor tendon laxity-and metabolic alterations such as hypoglycemia, neutropenia, and elevated lactate. Despite intensive care including plasma transfusions, nutritional support, and fluid therapy, the foal deteriorated and died at 72 hours. Biochemical analyses of peripheral markers confirmed metabolic and immune immaturity. This case highlights the clinical and prognostic challenges of induced parturition in mares, especially in the absence of objective markers of fetal maturity. Improved diagnostic methods are urgently needed to assess fetal readiness for birth and reduce neonatal morbidity and mortality in equine high-risk pregnancies.
Keywords:
equine reproduction; induced parturition; neonatal immaturity; fetal maturity assessment
RESUMO
Éguas apresentam um tempo de gestação variável, e a indução do parto, mesmo a termo, é limitada para gestações de alto risco devido à imprevisibilidade da maturidade fetal. Este relato descreve a indução de um parto em égua Puro-Sangue Inglês com laminite aguda aos 327 dias de gestação. O parto foi induzido mediante administração intravenosa de ocitocina, resultando em parto eutócico. Contudo, o potro apresentou sinais de imaturidade grave - ausência de reflexo de sucção, incapacidade de se levantar, frouxidão dos tendões flexores - e alterações metabólicas, como hipoglicemia, neutropenia e lactato elevado. Apesar dos cuidados intensivos, incluindo transfusões de plasma, suporte nutricional e fluidoterapia, o potro veio a óbito com 72 horas de vida. Análises bioquímicas sanguíneas confirmaram imaturidade orgânica e imunológica. Este caso evidencia os desafios clínicos e prognósticos da indução do parto em éguas, especialmente na ausência de marcadores objetivos de maturidade fetal. Métodos diagnósticos aprimorados são urgentemente necessários para avaliar a prontidão fetal para o nascimento e reduzir a morbidade e a mortalidade neonatal em gestações equinas de alto risco.
Palavras-chave:
reprodução equina; indução do parto; imaturidade neonatal; avaliação da maturidade fetal
INTRODUCTION
The considerable variability in equine gestation (320 to 360 days) complicates determining optimal timing for induced parturition (Nagel et al., 2014), making labor induction a contentious practice recommended only when maternal or fetal health is significantly compromised (Santschi and Vaala, 2011). Nevertheless, in the final days of gestation, a surge in fetal cortisol is responsible for the maturation of organ systems and the foal’s preparation for extrauterine life (Nagel and Aurich, 2022). However, high-risk pregnancies requiring induction prior to the natural hormonal maturation process can lead to neonates facing adaptation challenges, with a high incidence of complications and neonatal mortality (Ashraf, 2022).
In this context, a thorough assessment of readiness for birth is essential, considering indicators such as gestational duration, mammary development, colostrum production, and cervical changes. Even so, the absence of reliable diagnostic methods to ensure complete fetal maturity poses a significant clinical challenge. Organic immaturity, especially deficiencies in primary reflexes and thermoregulation, are common in equine neonates born through induced parturition (Curcio and Nogueira, 2012). These factors worsen the prognosis and demand intensive life-support interventions, increasing the complexity and risk associated with induction procedures in equines (Nagel et al., 2020).
This case report presents an induced parturition in a Thoroughbred mare with acute laminitis, focusing on the intensive neonatal care provided to the foal. The objective is to explore the complexities and challenges of labor induction in a high-risk pregnancy, assessing the clinical outcomes for the neonate and emphasizing the need for enhanced criteria to determine fetal maturity to improve neonatal prognoses in similar cases. Although the practice of inducing parturition is not novel, this case underscores the urgent need for robust criteria to assess fetal maturity. Our report highlights that current pre-induction assessments may be insufficient, thereby contributing to a growing discussion about the optimization of neonatal management in high-risk equine pregnancies.
ETHICAL ASPECTS
The research was submitted to the Ethics Committee on Animal Use of the Federal University of Pelotas and approved under the number # 23110.005810/2010-91.
CASUISTRY
A newborn Thoroughbred foal, female, was admitted to the Hospital de Clínicas Veterinárias at the Federal University of Pelotas (HCV - UFPel) at 24 hours old. According to the anamnesis, labour induction was performed on the farm at 327 days of gestation due to the mare’s acute laminitis, via intravenous administration of oxytocin (Oxitocin® 60 IU, IV). Approximately one hour later, the mare experienced eutocic foaling, and the foal exhibited evident signs of immaturity, including absence of a suckling reflex and inability to stand. According to further anamnesis, the following medications had already been administered on the farm: penicillin (Penfort®, Biofarm Química e Farmacêutica, 20,000 IU/kg IM), amikacin (Pareum®, UCBVET Saúde Animal, 20mg/kg IM), dexamethasone (Cortvet®, UCBVET Saúde Animal, 0.1mg/kg IM), dimethyl sulfoxide (DMSO®, Biofarm Química e Farmacêutica, 0.5g/kg IV), and 5% glucose solution (industrial formulation, Brazil; 2L IV). Additionally, colostrum (250mL) and 150mL of milk were administered via nasogastric tube at one-hour intervals. Dimethyl sulfoxide was used as an alternative approach to address potential central nervous system disturbances associated with neonatal maladjustment syndrome.
Upon arrival at the hospital, an initial clinical examination was conducted, including assessment of vital parameters and neurological response. The foal’s heart rate was 100 beats per minute (bpm), respiratory rate was 32 breaths per minute (bpm), capillary refill time (CRT) was 2 seconds, mucous membranes were pink, and body temperature was 38.2ºC. Intestinal motility was considered physiological in all abdominal quadrants. However, in the subsequent hours, the foal exhibited lethargy, absence of the suckling reflex, and inability to maintain sternal recumbency and stand unaided, due to bilateral laxity of the flexor tendon group with hyperextension of the metacarpophalangeal joint in both limbs.
Following the clinical assessment, thoracic and abdominal ultrasonography was performed, revealing comet-tail artefacts in the right lung lobe and reduced intestinal motility. Urethral catheterization was necessary to empty the bladder, yielding approximately 600mL of urine. For hematological and biochemical evaluation, whole blood samples were collected in EDTA and clot-activating tubes, allowing a comprehensive analysis of the foal’s serum parameters, essential for continuous clinical monitoring and subsequent therapeutic adjustments.
Initial therapy included administration of ampicillin (Ampicillin®, Biofarm Química e Farmacêutica, 22mg/kg IV, TID), meloxicam (Maxicam 2%®, Ouro Fino Saúde Animal Ltda., 0.6 mg/kg IV, SID), dexamethasone (Cortvet®, UCBVET Saúde Animal, 0.1mg/kg IM, SID), and metoclopramide hydrochloride (Plasil®, Sanofi-Aventis, 0.15mg/kg SC, QID). Fluid therapy was initiated with 5% glucose and lactated Ringer’s solution, supplemented with dimethyl sulfoxide (DMSO®, Biofarm Química e Farmacêutica, 0.5g/kg IV), vitamin C (Zoovit C®, Vetnil Indústria e Comércio de Produtos Veterinários Ltda., 5.0mL IV), and vitamin B complex (Bionew®, Biofarm Química e Farmacêutica, 3mL IV), aimed at correcting the metabolic imbalances observed.
To assess passive immune transfer, a Zinc Sulfate Turbidity Test (ZST) was conducted, revealing failure in passive transfer, necessitating plasma transfusion (2 liters), administered in two stages at 24 and 48 hours of life. At 48 hours of life, ultrasonography revealed comet-tail artefacts in the right lung lobe and low intestinal motility, with some segments of the small intestine showing no peristaltic movement. Through the nasogastric tube, episodes of gastric reflux were observed, with volumes ranging from 60mL to 1 liter, leading to the suspension of maternal milk administration. Bladder evacuation was managed via urethral catheterization, with urine volumes between 20mL and 1L. Manual rectal evacuation was also required due to low muscle tone and lack of peristalsis in the rectal ampulla. The foal was repositioned every two hours to prevent complications associated with prolonged recumbency.
The foal was closely monitored clinically. Throughout, the foal remained in a stuporous state, without appetite, exhibiting signs of hypothermia and fluctuating intestinal motility (Table 1). Due to severe immaturity, with worsening clinical and biochemical parameters, the prognosis was unfavorable, and despite intensive care, the foal progressed to death at 72 hours of life.
Subsequent biochemical examinations showed elevated serum levels of lactate, triglycerides, and cholesterol, while glucose, albumin, and GGT levels were below reference values (Duncan et al., 2020). Hematological and biochemical analyses were performed at two time-points, at 24 and 72 hours of life, and the results are detailed in Tables 2 and 3.
Aleman et al. (2019). Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age.
DISCUSSION
Inducing labor in mares represents a complex and high-risk decision in veterinary medicine, particularly in cases involving debilitating maternal conditions such as acute laminitis. The choice to induce labor at 327 days of gestation in this case was guided by the severity of the maternal disease, as prolonging the pregnancy could further compromise the mare's health and increase complications for both mare and foal. Laminitis can lead to severe consequences when not adequately managed in late gestation, impairing uteroplacental perfusion and nutrient-oxygen exchange to the fetus (Santschi and Vaala, 2011). This case exemplifies a frequent dilemma in equine veterinary medicine: prioritizing maternal health at the potential expense of foal maturity and survival.
Although oxytocin-induced labor is recommended in high-risk cases, it does not guarantee complete fetal maturity, particularly regarding adrenocortical development and extrauterine adaptability. Oxytocin in moderate doses (60 IU in saline) induces labor within 15-90 minutes, minimizing fetal exposure to compromised physiological conditions (Nagel and Aurich, 2022). However, this practice should be accompanied by careful assessment of fetal maturity markers, such as colostrum calcium concentration and udder development (Curcio and Nogueira, 2012). The absence of complete maturity signs in this case underscores that early induction without robust parameters often results in neonates with high degrees of dysmaturity and low survival capability.
Dysmature equine neonates frequently exhibit delayed intrauterine maturation, even within the 320-360-day gestation range. Final maturation of fetal organ systems occurs in the last days of gestation, primarily driven by increased fetal cortisol (Nagel and Aurich, 2022). Insufficient hypothalamic-pituitary-adrenal axis response results in deficiencies in thermoregulation, suckling ability, and physical stamina (Feijó et al., 2014). The foal's characteristics at birth-fine hair coat, domed forehead, inability to sustain sternal recumbency, and absent suckling reflex-indicate clinical dysmaturity (Morel, 2005).
This foal also displayed features consistent with neonatal maladjustment syndrome (NMS), associated with inadequate neurosteroid clearance and impaired transition to extrauterine life. Elevated progesterone levels beyond 24 hours postpartum correlate with persistence of neuroactive compounds that delay normal behavioral and neurological function (Aleman et al., 2019). DMSO, while not routinely employed in equine neonatology, was used for its potential to mitigate oxidative stress and support neurological recovery. While DMSO is known for anti-inflammatory effects, its role in neonatal equine care lacks rigorous research validation, and future studies should address this gap.
Biochemical and hematological evaluations revealed significant markers of immaturity. Elevated blood lactate indicates hypoxia and anaerobic metabolism associated with induced labor and perinatal stress (Castagnetti et al., 2010). The foal maintained high lactate levels, signaling metabolic incapacity for extrauterine adaptation. Low glucose and albumin levels indicate hepatic immaturity and insufficient gluconeogenic capacity, critical for neonatal energy support (Nagel et al., 2020). Given clear indicators of poor prognosis-including severe hypoglycemia, respiratory compromise, and immune immaturity-early discussion with owners regarding treatment failure versus humane euthanasia is essential.
Limb hyperextension, commonly observed in premature neonates, relates to flexor tendon fragility lacking adequate collagen and muscle tone, suggesting incomplete bone and joint maturity (Kidd and Barr, 2002). Low neutrophil counts and altered neutrophil-to-lymphocyte ratio suggest immature inflammatory response and inadequate immune function (Jeffcott et al., 1982). Neutropenia in premature neonates may be associated with adrenocortical insufficiency and low immune axis responsiveness.
Colostrum conductivity and pH have emerged as sensitive indicators for predicting parturition timing and guiding clinical decisions. Portable devices measuring these parameters enable real-time monitoring, supporting timely colostrum administration and passive immunity transfer-critical in induced parturition cases (Magalhaes et al., 2024). Labor induction should be preceded by comprehensive assessment of fetal maturity, incorporating biochemical markers (calcium carbonate >250 ppm, declining pH) and physical indicators (udder development, perineal relaxation, teat waxing) (Nagel and Aurich, 2022). Integrating objective indicators provides a reliable framework for determining optimal intervention timing and improving neonatal viability. Developing endocrine and biochemical biomarkers to assess adrenocortical axis and immune system maturity could significantly enhance predictive ability in high-risk pregnancies, reducing mortality rates and optimizing clinical outcomes (Nagel and Aurich, 2022).
CONCLUSIONS
This case underscores that gestational age alone is insufficient to determine fetal readiness for birth, and that inducing mares without objective evidence of fetal maturity significantly increases the risk of neonatal morbidity and mortality. Dysmature foals typically present with poor suckling reflex, tendon laxity, and metabolic derangements that require intensive supportive care, often with unsuccessful outcomes. To improve decision-making in high-risk pregnancies, reliable and field-applicable biomarkers-particularly colostral calcium levels and pH-should be prioritized before proceeding with labor induction. Veterinarians must carefully balance maternal health needs against neonatal viability and engage in early prognostic discussions with owners, ensuring informed decisions.
REFERENCES
- ALEMAN, M.; McCUE, P.M.; CHIGERWE, M. et al Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age. J. Vet. Intern. Med, v.33, p.2286-2293, 2019.
- ASHRAF, R. Normal, induced and difficult parturitions in equines - a review. Agrobiol. Rec, v.10, p.1-14, 2022.
- CASTAGNETTI, C.; PIRRONE, A.; MARIELLA, J. et al Venous blood lactate evaluation in equine neonatal intensive care. Theriogenology, v.73, p.343-357, 2010.
- CURCIO, B.R.; NOGUEIRA, C.E.W. Newborn adaptations and healthcare throughout the first age of the foal. Anim. Reprod, v.9, p.182-187, 2012.
- DUNCAN, N.B.; JOHNSON, P.J.; CROSBY, M.J. et al Serum chemistry and hematology changes in neonatal stock-type foals during the first 72 hours of life. J. Equine Vet. Sci, v.84, p.102855, 2020.
- FEIJÓ, L.S.; CURCIO, B.R.; ALVARENGA, F.C.L. et al Maturidade de potros nascidos de éguas com placentite. Arq. Bras. Med. Vet. Zootec, v.66, p.1662-1670, 2014.
- HARVEY, J.W., ASQUITH, R.L., McNULTY, P.K. et al Hematology of foals up to one year old. Equine Vet J, v. 16, p.347-353, 1984.
- JEFFCOTT, L.B.; ROSSDALE, P.D.; LEADON, D.P. Haematological changes in the neonatal period of normal and induced premature foals. J. Reprod. Fertil, v.32, p.537-544, 1982.
- KIDD, J.A.; BARR, A.R.S. Flexural deformities in foals. Equine Vet. Educ, v.14, p.311-321, 2002.
- MAGALHAES, H.B.; RAMIRES NETO, C.; OLIVEIRA, R.A. et al Conductivity of mammary gland secretions is a sensitive and specific predictor of parturition in mares. Equine Vet. J, v.56, p.719-725, 2024.
- MOREL, M. Management of the pregnant mare. In: _____Breeding horses [s.l.]: Wiley, 2005. p.111-134.
- NAGEL, C.; AURICH, C. Induction of parturition in horses - from physiological pathways to clinical applications. Domest. Anim. Endocrinol, v.78, p.106670, 2022.
- NAGEL, C.; AURICH, J.; AURICH, C. et al Parturition in horses is dominated by parasympathetic activity of the autonomous nervous system. Theriogenology, v.82, p.160-168, 2014.
- NAGEL, C.; MELCHERT, M.; AURICH, C. et al Differences in endocrine and cardiac changes in mares and her fetus before, during, and after parturition in horses of different size. Animals, v.10, p.1577, 2020.
- SANTSCHI, E.M.; VAALA, W.E. Management of the high-risk pregnancy. In: MCKINNON, A.O.; SQUIRES, E.L.; VAALA, W.E.; DICKSON D.; VARNER, D.D. Equine reproduction 2.ed. Oxford: Wiley-Blackwell, 2011. p.2262-2267.
The research data are available upon request.
