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  These ultrasound pictures represent the early stages of an equine pregnancy. An equine embryo can be located with the ultrasound as early as 10 days post ovulation (end of cycle). At 14 and 15 days (above left and right) the equine embryo is hard to miss. This "black circle" is the expanding, fluid portion of the embryo, and is perfectly round. The embryo is still moving within the mares uterus at this stage.
  By 18 days (above left) the embryo has lost its round character and is now beginning to attach to the mares uterus. At 22 days (above right) one can see the actual embryo (small white blip at about 5 o'clock position of the black oval) On the real time ultrasound if we look closely at that "white blip" one can easily see an embryonic heartbeat. From this point the embryo continues to develop at a very rapid pace.
 If a mare ovulates more than one egg (most common) or a single embryo divides (less common) we can end up with two embryos. The above picture shows two 16 day embryos basically stuck together. Since twins are undesirable in horses, our best option is to eliminate one of these embryos. I once observed three embryos on an early pregnancy exam of a mare that was naturally bred. I was able to eliminate two embryos, and she foaled normally the next spring.
All images copyright Dr. Larry D. Gertsch. No commercial use without written permission.  |
