Success rates and factors influencing pregnancy outcome after 464 transvaginal ultrasound-guided twin reductions in the mare.
Authors: Sielhorst Jutta, Baade Sophie, Neudeck Kim-Carolin, Tönissen Anna, Rohn Karl, Hollinshead Fiona, Sieme Harald
Journal: Equine veterinary journal
Summary
# Editorial Summary Transvaginal ultrasound-guided aspiration (TUA) is now a well-established technique for reducing twin pregnancies in mares, yet practitioners have had limited evidence regarding which factors optimise outcomes and whether success rates justify the procedure. This retrospective analysis examined 464 TUA procedures across 422 mares at two facilities over a decade, evaluating how gestational age, aspiration volume, conceptus puncture, medication protocols, embryo location, mare age, parity and operator experience influenced pregnancy retention and live foaling rates. The headline finding is that approximately 40% of mares achieved a live singleton foal overall, rising to 49.3% when TUA was performed between days 25–35 of gestation; only 57.2% of mares maintained a singleton pregnancy at 5–7 days post-procedure, with 27% losing both conceptuses entirely. For equine practitioners advising owners of twin-bearing mares, these results validate early intervention as the most evidence-based approach, though the substantial loss rate even with optimal timing—coupled with persistent twin pregnancies occurring in 15.8% of cases—warrants thorough informed consent discussions about realistic success probabilities and the need for continued monitoring throughout gestation.
Read the full abstract on PubMed
Practical Takeaways
- •TUA is an effective option for mares with dizygotic twins, with best outcomes when performed between days 25-35 of gestation; counsel owners on realistic expectations of ~49% live foal delivery rate
- •Early intervention before day 40 of gestation optimizes success rates compared to later procedures; establish clear gestation dating protocols for accurate timing
- •Standardize monitoring with ultrasound at 5-7 days and 3-4 weeks post-procedure to confirm singleton pregnancy status and plan appropriate management
Key Findings
- •Transvaginal ultrasound-guided aspiration (TUA) performed at days 25-35 of gestation resulted in live singleton foal delivery in 49.3% (74/150) of mares
- •At 5-7 days post-TUA, 57.2% (218/381) of mares achieved singleton pregnancy status
- •Overall foaling rate was 40.1% (127/317) of mares delivering a live single foal following TUA
- •Early gestation TUA (<40 days) achieved acceptable pregnancy and foaling rates in twin pregnancies, representing the first large-scale evidence for this procedure