Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction?
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.
Publication Date: 2023-01-03 PubMed ID: 36592981DOI: 10.1071/RD22239Google Scholar: Lookup
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Summary
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This research article discusses the causes of embryonic and foetal loss in horses, focusing on environmental factors, inherent embryo defects, and genetic variations potentially affecting foetal viability.
Overview of Equine Placental and Foetal Development
- The paper begins by introducing the crucial elements of foetal and placental development in horses. Understanding this development process is important, as deviations from the norm can lead to pregnancy loss.
Incidence and Risk Factors of Pregnancy Loss
- The authors discuss the rates and risk factors of pregnancy loss in horses. The incidence of embryonic and foetal loss in equine reproduction continues to be a significant challenge, with about 5-10% of pregnancies established day 15, and an additional 5-10% of pregnancies established day 70, not leading to a viable foal.
Causes of Pregnancy Loss
- The paper explores various reasons for these pregnancy losses. The causes can be broadly classified into two categories: environmental causes and intrinsic defects.
- Environmental causes refer to the conditions in which the embryo and subsequently the foetus develop. These include the nature of the maternal endometrium, endocrine factors, immune responses, and exposure to infectious pathogens.
- The second category is intrinsic defects within the embryo itself. These defects make the embryo non-viable, leading to loss at any stage of gestation and even right up until birth.
Role of Genetic Variants
- The paper also examines the role of both minor and major genetic variants in affecting foetal viability. This area of research is relatively new in equine reproduction studies, as historically the emphasis was on other factors such as maternal responses and infectious agents.
- The genetic variants mentioned could cause a range of issues in the development, survival, and viability of the horse embryo and later foetus, consequently resulting in pregnancy loss.
Overall, the article presents a multi-faceted investigation into the causes of pregnancy loss in horses, particularly focusing on the impact of various genetic variants on foetal viability.
Cite This Article
APA
Shilton CA, Kahler A, Roach JM, Raudsepp T, de Mestre AM.
(2023).
Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction?
Reprod Fertil Dev, 35(2), 51-69.
https://doi.org/10.1071/RD22239 Publication
Researcher Affiliations
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK.
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK.
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK.
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458, USA.
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK.
MeSH Terms
- Humans
- Animals
- Pregnancy
- Horses
- Female
- Placenta / pathology
- Fetus
- Embryo, Mammalian
- Abortion, Induced
- Abortion, Spontaneous
Citations
This article has been cited 2 times.- Lawson JM, Salem SE, Miller D, Kahler A, van den Boer WJ, Shilton CA, Sever T, Mouncey RR, Ward J, Hampshire DJ, Foote AK, Bryan JS, Juras R, Pynn OD, Davis BW, Bellone RR, Raudsepp T, de Mestre AM. Naturally occurring horse model of miscarriage reveals temporal relationship between chromosomal aberration type and point of lethality. Proc Natl Acad Sci U S A 2024 Aug 13;121(33):e2405636121.
- De Coster T, Zhao Y, Tšuiko O, Demyda-Peyrás S, Van Soom A, Vermeesch JR, Smits K. Genome-wide equine preimplantation genetic testing enabled by simultaneous haplotyping and copy number detection. Sci Rep 2024 Jan 23;14(1):2003.
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