Monozygotic multiple pregnancies after transfer of single in vitro produced equine embryos.
Authors: Dijkstra A, Cuervo-Arango J, Stout T A E, Claes A
Journal: Equine veterinary journal
Summary
# Editorial Summary: Monozygotic Multiple Pregnancies Following Equine IVP Embryo Transfer Monozygotic (identical) multiple pregnancies represent a significant but previously undercharacterised complication of in vitro embryo production in horses, occurring in 1.6% of transfers compared with no cases following in vivo embryo transfer in this retrospective analysis of 906 total embryos. The researchers transferred fresh in vivo and frozen-thawed intracytoplasmic sperm injection (ICSI)-derived blastocysts into recipient mares, documenting pregnancy establishment rates of 83% and 62% respectively, with monozygotic multiples appearing exclusively in the IVP cohort (4 cases: three sets of twins and one triplet). A critical diagnostic challenge emerged from the ultrasonographic findings: single embryonic vesicles were consistently observed during early pregnancy monitoring, with multiple embryonic bodies only becoming visible during later examinations for embryo proper and heartbeat development, or retrospectively following abortion. All four cases resulted in pregnancy loss—two twin pregnancies aborted at 3 and 9 months respectively, the triplet lost all three embryos before day 35, and attempted twin reduction by transrectal compression of one fetal thorax at day 50 resulted in loss of both fetuses. These findings highlight that IVP embryos carry an elevated risk of monozygotic splitting undetectable in early gestation, with delayed diagnosis contributing to substantial reproductive failure that may warrant more frequent or advanced ultrasonographic monitoring protocols in recipient mares carrying IVP conceptuses.
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Practical Takeaways
- •In vitro embryo production carries significantly higher risk of monozygotic twinning than natural embryo transfer; practitioners should counsel clients accordingly
- •Early ultrasound cannot reliably detect monozygotic multiples from IVP embryos; repeated scans during embryo proper development are essential to diagnose this complication before later pregnancy loss
- •Current management options for monozygotic multiple pregnancies from IVP embryos are ineffective; prevention through embryo selection or handling modification should be prioritized over intervention attempts
Key Findings
- •IVP embryos resulted in 1.6% (4/254) multiple pregnancy incidence compared to 0% (0/413) for in vivo embryos
- •Three cases of monozygotic twins and one case of triplets originated from single IVP embryos
- •Multiple embryonic bodies were undetectable on early ultrasound but became apparent only after embryo proper development
- •All four multiple pregnancies resulted in pregnancy loss: two twin pregnancies aborted at 3 and 9 months, triplet pregnancy lost all heartbeats by day 35, and twin reduction attempt resulted in loss of both fetuses