How common are twins in horses?

Twins in horses are considered extremely rare for several reasons related to the biology and reproductive habits of horses. Typically, horses are designed to have a single foal per pregnancy, and the physiological makeup of the mare's reproductive system supports this singular outcome effectively. When twin embryos do develop, there are significant risks both to the foals and the mare, as the mare may not have enough resources to support two developing foals.

Additionally, if twins are not detected early in the pregnancy, the mare is likely to abort one or both fetuses, leading to a very low live birth rate of twin foals. Research indicates that the occurrence of twin births in horses is significantly lower compared to other livestock, such as cattle or sheep. As a result, it is understood in the equine industry that while it is possible for a mare to conceive twins, it is not something commonly encountered, reinforcing the view that twin births in horses are extremely rare events.