In later pregnancy (four to five months onwards) it is possible to diagnose pregnancy by manual rectal palpation. This cannot identify twins.
In later pregnancy we can monitor the developing foal and placenta by trans-abdominal ultrasound examination. This can allow identification of problems in late pregnancy such as infection (placentitis).
Three ultrasound examinations are advised:
Further or additional scans may be advised if twins are identified and one conceptus manually reduced, to check that only one pregnancy remains.
If only one pregnancy scan is to be carried out then a scan between 21 and 34 days of pregnancy is advised, although if twins are identified at this stage it is much more difficult to treat and much more likely to result in the loss of both embryos if this is attempted.
Later scans can be carried out but after day 90 the pregnancy begins to drop down in the abdomen and transrectal ultrasound is much less useful.
Once the pregnancy is established then it is possible to take blood from the mare to see if she is pregnant.
There are two main hormones that are measured depending on the stage of pregnancy:
This detects pregnancy from around 110 days to close to term. It is produced by the developing foal so a positive result indicates a live foal.
This can detect pregnancy from around day 45 – day 90. This is produced by the mare from the endometrial ‘cups’. If the mare loses the pregnancy then this hormone will remain high for some time, therefore it does not necessarily identify a live foal.
There is a time gap between day 90-120 when none of the blood tests are very accurate and false negatives may occur if mares are blood sampled in this window.
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