Fetal morphological features and abnormalities associated with equine early pregnancy loss.
Authors: Kahler Anne, McGonnell Imelda M, Smart Harriette, Kowalski Alycia A, Smith Ken C, Wathes D Claire, de Mestre Amanda M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Fetal morphological features and abnormalities associated with equine early pregnancy loss Early pregnancy loss affects roughly 8% of equine pregnancies, yet the underlying causes remain largely unclear. Kahler and colleagues conducted a case-control study comparing the morphology of 27 embryos and fetuses lost during early pregnancy with 11 clinically normal control specimens, measuring crown-rump length, assessing developmental stage macroscopically and microscopically, and correlating these findings with gestational age. Critically, the mismatch between size and age emerged as a defining feature of pregnancy loss—whilst age and crown-rump length showed a strong positive correlation in healthy pregnancies (R = 0.9), this relationship completely broke down in lost pregnancies (R = 0.1), with three of eight fetuses demonstrating clear intrauterine growth retardation. Microscopical examination revealed that 9 of 13 embryos and fetuses displayed non-specific alterations in developing neural tissue (including disruption of the brain stem regions) with evidence of premortem haemorrhage, whilst subcutaneous bleeding was present in over half the losses and one specimen showed failed neural tube closure. For practitioners, these findings highlight that a disparity between expected fetal size and breeding history warrants thorough investigation, and that neural developmental abnormalities and vascular compromise appear as common pathological features rather than incidental findings—though the authors note that autolysis complicated assessment in over half their loss cases, limiting definitive conclusions about true prevalence.
Read the full abstract on PubMed
Practical Takeaways
- •When investigating early pregnancy loss in mares, morphological examination can reveal specific abnormalities (neural tissue disruption, subcutaneous haemorrhage) that may help identify causes beyond infectious or hormonal factors
- •Mismatch between fetal size and gestational age is a key diagnostic indicator of early pregnancy loss and should prompt further investigation for developmental abnormalities
- •Although rare, neural tube closure failures occur in equine EPL; routine morphological assessment of lost pregnancies contributes to understanding the aetiology of EPL in your practice population
Key Findings
- •Early pregnancy loss embryos/fetuses showed no correlation between age and crown-rump length (R=0.1) compared to strong correlation in normal pregnancies (R=0.9)
- •Intrauterine growth retardation was identified in 3/8 EPL fetuses assessed, with smaller crown-rump length relative to controls
- •Neural tissue alterations including disruption of developing brain regions and haemosiderin deposits were found in 9/13 EPL embryos/fetuses examined microscopically
- •Subcutaneous haemorrhage was present in 14/27 EPL embryos/fetuses, and failed neural tube closure was identified in 1/13 EPL cases