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Reproduction, Fertility and Development Reproduction, Fertility and Development Society
Vertebrate reproductive science and technology
REVIEW (Open Access)

Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction?

Charlotte A. Shilton A , Anne Kahler A , Jessica M. Roach A , Terje Raudsepp B and Amanda M. de Mestre A *
+ Author Affiliations
- Author Affiliations

A Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK.

B Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458, USA.

* Correspondence to: ademestre@rvc.ac.uk

Reproduction, Fertility and Development 35(2) 51-69 https://doi.org/10.1071/RD22239
Published online: 7 November 2022

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS. This is an open access article distributed under the Creative Commons Attribution 4.0 International License (CC BY)

Abstract

Embryonic and foetal loss remain one of the greatest challenges in equine reproductive health with 5–10% of established day 15 pregnancies and a further 5–10% of day 70 pregnancies failing to produce a viable foal. The underlying reason for these losses is variable but ultimately most cases will be attributed to pathologies of the environment of the developing embryo and later foetus, or a defect intrinsic to the embryo itself that leads to lethality at any stage of gestation right up to birth. Historically, much research has focused on the maternal endometrium, endocrine and immune responses in pregnancy and pregnancy loss, as well as infectious agents such as pathogens, and until recently very little was known about the both small and large genetic variants associated with reduced foetal viability in the horse. In this review, we first introduce key aspects of equine placental and foetal development. We then discuss incidence, risk factors and causes of pregnancy loss, with the latter focusing on genetic variants described to date that can impact equine foetal viability.

Keywords: abortion, aneuploidy, chromosome, CNV, early pregnancy loss, embryology, equine, fetus, genetics, horse, mare, miscarriage, monosomy, placenta, pregnancy complications, pregnancy loss, SNPs, translocation, trisomy, trophoblast.


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