Factors Affecting Survival and Future Foaling Rates in Thoroughbred Mares with Hydrops.
Authors: Lemonnier Louise C, Wolfsdorf Karen E, Kreutzfeldt Nicole, Fedorka Carleigh, Chigerwe Munashe, Bozorgmanesh Rana
Journal: Journal of equine veterinary science
Summary
# Hydrops in Thoroughbred Mares: Survival and Fertility Outcomes Hydrops—an excessive accumulation of fluid in the amniotic or allantoic sac—has long been considered a manageable condition in broodmares, yet empirical evidence supporting this optimistic view remained sparse. This case series reviewed 30 Thoroughbred mares presenting with hydrops between 2009 and 2019 to establish realistic prognostic data for both survival and subsequent reproductive performance. Overall survival reached 90% (27/30), with hydrallantois showing superior outcomes at 94.7% compared to hydramnios at 75%, and critically, 95% of surviving mares (20/21) subsequently produced viable foals, with three-quarters conceiving again within 12 months and no cases of recurrent hydrops. Transcervical gradual fluid drainage proved instrumental in improving survival rates, achieving 100% success versus 78.6% without this intervention; conversely, complications including hypovolaemic shock, haemorrhage and laminitis directly correlated with non-survival and reproductive failure. These findings validate the generally optimistic prognosis, provided cases are identified early and managed with appropriate techniques—particularly fluid drainage—and that no structural damage occurs to the reproductive tract or abdominal wall, making prompt diagnosis and intervention crucial for practitioners managing in-foal mares presenting with abdominal distension and respiratory compromise.
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Practical Takeaways
- •Hydrops carries a good prognosis for both survival and future fertility when diagnosed early and managed with transcervical gradual fluid drainage, with no observed recurrence in this series
- •Hydrallantois responds better to treatment than hydramnios; prioritize transcervical drainage to avoid serious complications like hypovolemic shock and hemorrhage that compromise both survival and breeding potential
- •Expect approximately 71% of mares to foal the following year after hydrops treatment, allowing informed breeding and management decisions for affected broodmares
Key Findings
- •90% of mares with hydrops survived to discharge (27/30), with 94.7% survival in hydrallantois cases versus 75% in hydramnios cases
- •95% of surviving mares (20/21) successfully returned to breeding with no recurrence of hydrops, and 71% foaled within one year
- •Transcervical gradual fluid drainage increased survival to 100% versus 78.6% in mares without this intervention
- •Non-survival was associated with peritonitis from abdominal wall rupture or uterine tear, while complications preventing return to breeding included hypovolemic shock and hemorrhage