Very Common
Less Common
OTHER DIAGNOSES CONSIDERED
Other conditions or ailments that might also need to be ruled out by a vet.
Diagnosis
Conditions or ailments that are the cause of a problem that you see - your observation.
Your vet may diagnose
Twin Embryos or Fetuses Detected on Ultrasound
Summary
Twin conceptions are surprisingly common in mares, and result from multiple ovulation of follicles from the ovaries. Both eggs are fertilized by semen in the uterus, and two embryos form. The twin embryos move independently around the uterus for about 16 days after fertilization, and then attach to the wall of the uterus.
Twinning is more common in Thoroughbred, Warmblood and Draft Horse mares and in young to middle aged mares.
About 50% of twin pregnancies naturally reduce to one fetus, called a singlet. Often, one embryo resorbs (disappears) without incident. This natural reduction is more common when twins are implanted in the same uterine horn than when they are in different horns.
If both pregnancies survive into mid to late gestation, often the smaller fetus becomes distressed, causing premature labor and abortion of both pregnancies. This usually happens between 7-10 months of gestation. In rare cases, twins are born full term, alive, and survive.
The standard diagnostic test for twins is veterinary trans-rectal ultrasound at 14-20 days gestation. Twin embryos can be confused in this early ultrasound with uterine cysts. If there is any doubt about the presence of twins, repeat ultrasound exam may be needed. Twins can also be detected later in pregnancy either by rectal palpation or more commonly ultrasound, but the diagnosis is much more difficult and there is little one can do other than terminate the entire pregnancy.
When diagnosed early, one of the embryos can be eliminated, allowing the other to survive.
TREATMENT- The most common and effective method for reduction of twins to a singlet is manual, trans-rectal reduction of the embryos through crushing, usually under ultrasound guidance.
Twinning is more common in Thoroughbred, Warmblood and Draft Horse mares and in young to middle aged mares.
About 50% of twin pregnancies naturally reduce to one fetus, called a singlet. Often, one embryo resorbs (disappears) without incident. This natural reduction is more common when twins are implanted in the same uterine horn than when they are in different horns.
If both pregnancies survive into mid to late gestation, often the smaller fetus becomes distressed, causing premature labor and abortion of both pregnancies. This usually happens between 7-10 months of gestation. In rare cases, twins are born full term, alive, and survive.
The standard diagnostic test for twins is veterinary trans-rectal ultrasound at 14-20 days gestation. Twin embryos can be confused in this early ultrasound with uterine cysts. If there is any doubt about the presence of twins, repeat ultrasound exam may be needed. Twins can also be detected later in pregnancy either by rectal palpation or more commonly ultrasound, but the diagnosis is much more difficult and there is little one can do other than terminate the entire pregnancy.
When diagnosed early, one of the embryos can be eliminated, allowing the other to survive.
TREATMENT- The most common and effective method for reduction of twins to a singlet is manual, trans-rectal reduction of the embryos through crushing, usually under ultrasound guidance.
my vet's role
Diagnostics Used
These are tests that might be helpful to make this diagnosis or further characterize the condition.
Treatments May Include
These treatments might be used to help resolve or improve this condition.
Very Common
Less Common
PROGNOSIS AND RELEVANT FACTORS
The prognosis is good if a twin can be eliminated by about day 25. After that, it becomes increasingly harder to reduce twins without terminating the entire pregnancy.Mares that give birth to twins are likely to abort. If they do go to near term or term, then retained placenta and uterine infection are relatively common. In most cases, one or both twin foals are born dead. if they are born alive, they tend to be small and somewhat stunted.
my role
I might observe
You might make these observations when a horse has this condition.
Very Common
Questions To Ask Your Vet:
- What method can be used to reduce twins to a singlet in this case?
- What are the chances of successful reduction to one fetus?
- Are you sure that these are twins, and that this is not a uterine cyst?
Prevention
Recognize how common twin pregnancies are and understand the reasons why they are undesirable.
Your vet should perform an ultrasound at day 14-16 post-ovulation, searching for twins. A second ultrasound should be performed at between 40 and 50 days post-ovulation to ensure that the surviving singlet pregnancy is alive and well.
Mares that have had twins will likely twin again. Your vet will check and double check mares with that history to be sure there are not twins.
further reading & resources
Helpful Terms and Topics
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