Changes

Also Known As – '''''Twinning'''''

Also Known As – '''''Twinning'''''

Due to the nature of the equine [[Placenta - Anatomy & Physiology|placenta]], which is dependent upon surface area of attachment, '''the majority of twin pregnancies are not viable as placentation is inadequate''', and therefore they result in '''abortion of one or often both foetuses.'''

Due to the nature of the equine [[Placenta - Anatomy & Physiology|placenta]], which is dependent upon surface area of attachment, '''the majority of twin pregnancies are not viable as placentation is inadequate''', and therefore they result in '''abortion of one or often both foetuses.'''

Embryos in the horse are '''mobile until approximately day 15 of pregnancy''', a key event for [[Maternal Recognition of Pregnancy - Anatomy & Physiology]], at which point they implant in one of the uterine horns. '''75% of twins that fixate in the same uterine horn will naturally reduce to a single pregnancy'''.<ref name="Blackwell">Lavoie, J-P., Hinchcliff, K. W (2008) '''Blackwell’s Five-Minute Veterinary Consult: Equine 2nd ed'''. ''Wiley-Blackwell, Oxford'', pp 780-781</ref> This does not occur when conceptuses implant in separate horns.

Embryos in the horse are '''mobile until approximately day 15 of pregnancy''', a key event for [[Maternal Recognition of Pregnancy - Anatomy & Physiology|maternal recognition of pregnancy]], at which point they implant in one of the uterine horns. '''75% of twins that fixate in the same uterine horn will naturally reduce to a single pregnancy'''.<ref name="Blackwell">Lavoie, J-P., Hinchcliff, K. W (2008) '''Blackwell’s Five-Minute Veterinary Consult: Equine 2nd ed'''. ''Wiley-Blackwell, Oxford'', pp 780-781</ref> This does not occur when conceptuses implant in separate horns.

Twin pregnancies may still be the '''most common cause of abortion in mares.'''

Twin pregnancies may still be the '''most common cause of abortion in mares.'''

If this procedure is used '''after 30 days of gestation then the fluid released is more likely to disrupt''' the remaining pregnancy. If both conceptuses have already implanted in the same horn of the uterus, it can be very difficult to crush one without also damaging the other. '''Survival rates fall significantly and progressively after 30 days of gestation. At 30 days, 85%''' of singleton foetuses are carried successfully to term.

If this procedure is used '''after 30 days of gestation then the fluid released is more likely to disrupt''' the remaining pregnancy. If both conceptuses have already implanted in the same horn of the uterus, it can be very difficult to crush one without also damaging the other. '''Survival rates fall significantly and progressively after 30 days of gestation. At 30 days, 85%''' of singleton foetuses are carried successfully to term.

Management after endometrial cup formation at 40 days is obviously very difficult, as it any pregnancy loss at this stage of gestation.  

Management after endometrial cup formation at 40 days is obviously very difficult, as it may cause pregnancy loss at this stage of gestation.  

'''Other possible options for reduction''' of one twin have been used, including dietary restriction, surgical removal, intracardiac injection of potassium chloride and transvaginal allantocentesis but are far less frequently used than manual reduction early in gestation due to lower success rates.

'''Other possible options for reduction''' of one twin have been used, including dietary restriction, surgical removal, intracardiac injection of potassium chloride and transvaginal allantocentesis but are far less frequently used than manual reduction early in gestation due to lower success rates.

{{Learning

{{Learning

|flashcards = [[Twin Pregnancies in Horses Flashcards]]

|flashcards = [[Twin Pregnancies in Horses Flashcards]]<br>[[Equine Reproduction and Stud Medicine Q&A 05]]

}}

}}

Merck Veterinary Manual, '''Management of Reproduction: Horses: Abortion''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/181607.htm

Merck Veterinary Manual, '''Management of Reproduction: Horses: Abortion''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/181607.htm

   

   

[[Category:To Do - Manson review]] [[Category: Reproductive Diseases - Horses]]

 

 

 

[[Category:Expert Review - Horse]] [[Category: Reproductive Diseases - Horse]]