Pregnancy outcome after transvaginal ultrasound-guided twin reductions

Success rates and factors influencing pregnancy outcome after 464 transvaginal ultrasound-guided twin reductions in the mare
Equine Vet J. 2024 Feb 14. doi: 10.1111/evj.14071. Online ahead of print.
Authors
Jutta Sielhorst 1 2 , Sophie Baade 2 3 , Kim-Carolin Neudeck 3 , Anna Tönissen 2 , Karl Rohn 4 , Fiona Hollinshead 5 , Harald Sieme 2
Affiliations

1 ReproTraining, Verl, Germany.
2 Unit for Reproductive Medicine-Clinic for Horses University of Veterinary Medicine Hanover, Foundation, Hanover, Germany.
3 Veterinary Clinic Karthaus, Duelmen, Germany.
4 Institute of Biometry, Epidemiology and Information Processing, University of Veterinary Medicine Hanover, Foundation, Hanover, Germany.
5 College of Veterinary Medicine and Biomedical Science, Colorado State University, Fort Collins, Colorado, USA.

PMID: 38353172
DOI: 10.1111/evj.14071

Abstract

Background: Transvaginal ultrasound-guided aspiration (TUA) is used for post-fixation twin reduction in mares. However, there is limited information regarding factors that influence pregnancy outcome after TUA.

Objectives: To evaluate the effect of day of gestation on which TUA is performed, aspiration volume, puncture of the conceptus, medication administered before and after TUA, embryo location, mare age and parity and operator experience on pregnancy and foaling rates after TUA.

Study design: Retrospective case series.

Methods: Data were collected from case records of 464 TUAs performed by 14 operators in 422 mares diagnosed pregnant with dizygotic twins in two different facilities between 2010 and 2019. Pregnancy status was determined by ultrasonography at 5-7 days and 3-4 weeks after the TUA was performed. Subsequent pregnancy and foaling results were obtained by follow-up communication. The effects of mare, gestation- and TUA-related variables on pregnancy and foaling rates were analysed by the chi-square-test for homogeneity and Fisher’s exact test and logistic regression.

Results: TUA was performed between 21 and 82 days of gestation in unilaterally (267/359 [74.4%]) and bilaterally fixed (92/359 [25.6%]) twin pregnancies. A singleton pregnancy (218/381 [57.2%]), persistent twin pregnancy (60/381 [15.8%]), or the loss of both conceptuses (103/381 [27%]) was confirmed 5-7 days after TUA was performed. At 3-4 weeks post TUA 50.3% (163/324) of mares were diagnosed with a single viable pregnancy and 40.1% (127/317) went on to deliver a live single foal. TUA performed early in gestation (D 25-35) resulted in the birth of a live singleton foal in 49.3% (74/150) of mares.

Main limitations: Missing retrospective data despite extensive follow-up.

Conclusion: This is the first large scale study to demonstrate that acceptable pregnancy and foaling rates can be achieved in mares diagnosed with twins when TUA is performed early in gestation (<40 days).

Keywords: foaling rate; horse; mare; pregnancy rate; transvaginal ultrasound-guided aspiration; twin pregnancy.

© 2024 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.