Pregnancy testing is commonly performed at 14, 30 and 45 days post ovulation. For mares where an ovulation check has not been performed a rough guide for the first pregnancy test is 15-16 days after the last service.

At 14 days post ovulation the pregnancy(s) are visible as a small approximately 1 cm fluid filled sac (vesicle). At this stage the pregnancy is still moving around the uterus. If twin pregnancies are detected one of the pregnancies may be reduced with a high chance of the other pregnancy surviving. (Please note that twin pregnancy in mares has a high complication rate often leading to loss of one or both foals and possible foaling complications for the mare. If detected it is generally recommended that the pregnancy be reduced to a singleton if possible or if not possible that both pregnancies be aborted.)

At 30 days post ovulation the pregnancy(s) are visible as fluid filled sacs with an embryo and its heartbeat can also been seen. It is still possible to reduce twin pregnancies to a singleton but there is a higher chance of losing both the pregnancies in that attempt. If a problem is detected with the pregnancy it is possible to use medication to abort the pregnancy with a high chance of the mare coming back in season for service.

At 45 days post ovulation the pregnancy(s) are visible as fluid filled sacs with the embryo and its heartbeat. It is much more difficult to reduce twin pregnancies to a single pregnancy at this stage, and even if the pregnancy is aborted using medication the mare may not come back in season for several months.

If pregnancy examination is performed after 45 days it becomes more difficult to detect twin pregnancies as the increasing size of the uterus and foetus makes it difficult to scan the entire uterus.

Of course the above ultrasound exams are by no means compulsory but as you can see there is a reason for each of them!

If ultrasound examination is not performed it is possible to evaluate pregnancy status by other methods such as ‘teasing’ the mare when it is anticipated she would be in season after service. There are also blood and urine tests available that determine the presence of hormones produced at different stages of pregnancy. Please note that these methods of pregnancy testing will not detect twin pregnancies, and they are not infallible.

Our vets are experienced in follicle testing and pregnancy testing in mares, including achieving pregnancy in ‘harder to get in foal’ mares. Please do not hesitate to call us and arrange a consult to develop a breeding plan for your mare.

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