Maternal dexamethasone treatment in late gestation induces precocious fetal maturation and delivery in healthy Thoroughbred mares.

This research investigates if synthetic glucocorticoids, specifically dexamethasone, can safely induce early fetal maturation and delivery in pregnant Thoroughbred mares. The researchers found that dexamethasone was effective in expediting delivery without apparent side effects. However, it may cause a decrease in hypothalamo-pituitary-adrenal (HPA) activity in the fetus, which further research needs to evaluate before clinicians can use this treatment.

Objective and Methods

• The research aimed to understand if dexamethasone given to pregnant mares in late gestation would induce early fetal maturation and delivery and monitor any adverse impacts. Secondary objectives were to track the endocrine responses in both mares and foals. Primarily, the study’s purpose was to explore potential ways to improve foal viability in cases of high-risk mares that might deliver prematurely.
• For the experiment, pregnant Thoroughbred mares were divided into two groups; one group received 100 mg dexamethasone while the other received 50 ml saline at specific days of the gestation period. The researchers monitored plasma progestagens, cortisol, and prostaglandin F(2α) metabolite concentrations before and after the treatment. Foal attributes like weight were recorded and an adrenal stimulation test was conducted on the first day.

Results

• Findings showed that dexamethasone significantly shortened the gestation period in treated mares without any noticeable adverse effects. Post-treatment, plasma progestagens rose while cortisol and PGFM dropped when compared to control mares. Foals from the dexamethasone group were clinically mature but had less crown-rump length. However, their body weights were not significantly different from the control group foals.
• The research also observed that cortisol concentrations increased in foals after the exogenous adrenocorticotrophic hormone stimulation. Nevertheless, two foals from the dexamethasone group showed signs of adrenal suppression.

Conclusions

• The findings conclude that dexamethasone does stimulate early fetal maturation and delivery in healthy late pregnant mares. However, it could suppress fetal HPA activity, which necessitates further investigation.
• The implications of this study suggest that dexamethasone treatment could enhance foal viability in high-risk mares prone to preterm delivery. However, the endocrine impacts of this intervention must be evaluated thoroughly before recommending clinical intervention with glucocorticoids.