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Genetics of early placental development and early pregnancy loss

Funded by the , United Kingdom

Early pregnancy loss (EPL) occurs in 7-10% of Thoroughbred (TB) pregnancies making it one of the most significant contributors to reproductive wastage in the United Kingdom’s TB industry. Despite the considerable economic losses associated with this condition, the cause of EPL is identified in less than 25 % of cases. Human studies show genetic causes account for between 40-90% of first trimester losses in women, however, the importance and implications of genetic changes in early equine pregnancy remain unknown.

Recent investigations in the laboratory have, for the first time, identified a method to isolate and culture placental cells from failed pregnancies. Preliminary investigations on 12 of these pregnancies identified 83 areas along the chromosome showing variations in the amount of genetic material when compared to normal adult thoroughbreds. Of these regions, 17 had never before been identified as areas of genetic variation in TBs. The aim of the current project is to investigate genetic causes of EPL. Normal genetic changes occurring throughout placental development will be identified and these findings used as a basis to identify genetic abnormalities in failed pregnancies. Blood samples from mares and sires together with an analysis of pedigrees will help to identify a hereditary component to EPL. Finally, analysis of specific areas of the genome will be carried out to determine if specific abnormalities or variations may render the pregnancy susceptible to viral invasion, in particular Equine Herpes Virus (EHV) which we have shown to be present in placental tissue from early pregnancies. The contribution of EHV to failure of equine pregnancy in the early stages is unknown but it is well recognised as a cause of equine abortion in later stages of pregnancy. The combined results of this study may enable the development of genetic tests to be used as diagnostic tools to determine the cause of EPL. Additionally, determination of the hereditary aspects of this condition may allow the prediction of the risk of EPL with certain mating combinations potentially allowing breeders to more accurately select mare/sire crosses to reduce the risk of pregnancy failure. By investigating novel causes of EPL this study will provide valuable information to enhance our knowledge of the condition which is essential if we are to reduce its prevalence and the associated economic and management implications.

The first findings from this project can be found in Scientific Reports via this open access link 

4 year grant funded by  PhD student Jessica Roach BVetMed MRCVS

Approximately 5-10% of pregnancies result in abortion or stillbirth making these losses a significant contributor to reproductive wastage in Thoroughbreds. The most common reported reason for abortion and stillbirths in the last extensive review published in the UK (2003) was twisting of the umbilical cord and long cords (38.8% of all abortions/stillbirths). Despite the high incidence of this condition in the UK, there is very little up to date research as to the risk fac