Horse Side Vet Guide ®

Equine Health Resource

Twin Fetuses Aborted or Stillborn

Code Red - Call Your Vet Immediately, Even Outside Business Hours

Code Red - Call Your Vet Immediately, Even Outside Business Hours

  • If the mare has also retained her placenta for longer than 3 hours.
  • Questions coming up around foaling should usually be discussed right away with your vet.

Twin embryos are a common cause of mid to late term abortion in mares. Only rarely are twin foals born alive and viable. The lifeline of the equine fetus is a velcro-like attachment of the placenta to the surface of the mare’s uterus. This puts the foal’s circulation in contact with that of the mare’s for exchange of nutrients.

In twin pregnancies, each fetus has its own individual placenta that must compete with that of the other for precious attachment surface area on the uterine lining. As each fetus matures in late gestation, its metabolic demands become greater and greater. Finally, one or both of the competing fetuses become stressed and signal the mare to deliver, usually prematurely.


If your mare has aborted twin fetuses, assess the mare’s general health first using the Whole Horse Exam on Post-Foaling Mare (WHE), paying particular attention to her attitude, appetite, heart rate, gum (mucous membrane) color, and temperature. Assess the vulva for tears or swelling, due to a difficult birthing process (dystocia). If both placentae are shed, do they look complete?

The birth of a small stillborn fetus at 8-10 months of gestation is always cause to consider that there may be a second fetus still in the mare. Retained placenta and subsequent uterine infection is a risk after twin abortion.


In this situation, your mare’s general health and reproductive health should be evaluated by a vet, who may suggest diagnostics to determine the cause of the abortion. By identifying the cause, you and your vet may be able to limit future damage to your mare’s reproductive health, ensure fertility for rebreeding, or even protect other broodmares in the group (assuming the diagnosis relates to an outside environmental cause).

Author: Doug Thal DVM Dipl. ABVP


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