Changes

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.'''