Maternal dexamethasone treatment in late gestation induces precocious fetal maturation and delivery in healthy Thoroughbred mares.
Authors: Ousey J C, Kölling M, Kindahl H, Allen W R
Journal: Equine veterinary journal
Summary
# Editorial Summary Synthetic glucocorticoids have long been used in human obstetrics to accelerate fetal organ maturation before anticipated preterm delivery, but their application in equine practice remains limited. Ousey and colleagues investigated whether dexamethasone administration in late gestation could safely induce fetal maturation and precocious parturition in Thoroughbred mares, administering either 100 mg dexamethasone or saline to five mares each at days 315–317 of pregnancy and measuring maternal and foetal endocrine markers alongside foal development indicators. Dexamethasone-treated mares delivered significantly earlier without observable clinical complications, and whilst foals appeared clinically mature with normal bodyweights, those from treated mares showed reduced crown-rump length and, concerning, evidence of suppressed adrenal responsiveness in two individuals following ACTH stimulation testing on day one post-partum. The findings suggest dexamethasone could theoretically benefit mares at high risk of spontaneous preterm delivery by promoting timely maturation, yet the potential for iatrogenic foetal HPA axis suppression warrants considerable caution before implementation in clinical settings.
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Practical Takeaways
- •Dexamethasone can effectively induce earlier delivery in pregnant mares at risk of complications, but requires careful evaluation of neonatal adrenal function before routine clinical use
- •Foals born after maternal dexamethasone treatment appear clinically mature despite potential suppression of their own adrenal response—monitor early neonatal cortisol responses and stress tolerance
- •This technique may improve foal survival in high-risk pregnancies, but endocrine consequences must be fully characterized and managed in practice
Key Findings
- •Maternal dexamethasone (100 mg i.m. at days 315-317 of gestation) significantly reduced gestation length in treated mares (P<0.01) without apparent adverse effects
- •Dexamethasone treatment increased plasma progestagens (P<0.05) and decreased cortisol and PGFM concentrations (P<0.05) compared to controls
- •Foals from treated mares showed clinical maturity but reduced crown-rump length (P<0.05) and 2 of 5 displayed evidence of adrenal suppression on ACTH stimulation testing
- •Dexamethasone stimulates precocious fetal maturation and delivery but may suppress fetal hypothalamo-pituitary-adrenal axis activity