Horse Side Vet Guide ®

Equine Health Resource

Twin Embryo Management



Twin pregnancies in horses is common but undesirable. In a normal pregnancy, a single fetus is surrounded by a diffuse placenta, its source of nourishment from the mare. It has the entire placenta all to itself.

Twin fetuses have to share this space, and the reduced placental surface area does not give both fetuses what they need to survive. Twin fetuses are usually naturally reabsorbed or aborted before term. If born, twin foals often die shortly after birth or do poorly.

Generally, a twin pregnancy can be diagnosed within 14-16 days of ovulation with rectal palpation and a transrectal ultrasound. If twins are detected early, vets try to eliminate one of them for the good of the other. The twins are reduced to a “singleton.”

The procedure involves grasping one of the embryonic vesicles through the rectal and uterine walls and putting pressure on it until it ruptures. The other embryo is left to develop normally.

If twins are detected later in a pregnancy, more invasive treatments are required and the pregnancy may need to be terminated.

Related DiagnosesThis Treatment Might Be Used for these Diagnoses

Consider Potential Side Effects & Complications

Possible loss of the remaining embryo, and the termination of the pregnancy. The rupture of one embryo disrupts the uterus, and may cause the pregnancy to be lost.

Consider Reasons Not To Use This Treatment

Early embryo rupture is not advised when the twins are too close together. If the pregnancy is less than 16 days, vets may choose to allow the embryos to move over a period of hours to days and recheck to see if they are in a better position for this treatment.

Is It working? Timeframe for effect

Assess viability of the remaining fetus in 1 week.

Questions To Ask My Vet

  • What is the danger to the mare in terminating the pregnancy?
  • What is the danger to the mare in eliminating the twin?

Helpful Outside ResourcesCredible Equine Health Information on the Internet

Author: Doug Thal DVM Dipl. ABVP


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