Horses usually only have one baby at a time. Twins do occasionally occur, but they are rare. A twin pregnancy often results in spontaneous abortion or in the death of one or both foals.
Modern veterinary science allows horse owners to abort one equine fetus if twins occur, so horses giving birth to twins is extremely rare. Veterinarians recommend this practice to avoid dangerous late-term spontaneous abortion, which results in the loss of both fetuses and potential injury to the mare. When twin foals are carried to term and successfully born, they are often small and sickly compared to healthy single foals. Larger breeds are more likely to carry twins successfully than small breeds and ponies.