Fetal death, eCG; the MIP test
Keywords equine, MIP, endometrial cups, infertilityEndometrial cups usually persist if fetal death occurs after 35 to 40 days of gestation. For unknown reasons, persisting production of eCG often causes failure to return to cyclicity or protracted periods of irregular estrous cycles. Even when a live foal is produced after an apparently normal pregnancy, endometrial cups and eCG production may persist, sometimes causing disruption of "foal heat" ovulations.
Endometrial cups are difficult to see using ultrasonography and one may not possess an endoscope. Therefore it may be necessary to rely on endocrinological tests to ascertain if endometrial cups are still present. It is most common to measure eCG by radioimmunoassay or ELISA but one may still find this old test in use:
It is a hemagglutination inhibition test, also knows and the mare immunopregnancy (MIP) test, a qualitative assay for eCG. In this illustration, the set of tubes on the right side have produced a positive test result. Endometrial cups were present in this mare. They can be seen on the endoscopic view at extreme right. It should be emphasized that the primary reason for marketing this test was to detect pregnancy, not to diagnose the persistence of endometrial cups. It can be seen however, that the MIP test was prone to false positives because a mare could still test positive for pregnancy after fetal death had occurred.
The image on the left hand side shows a negative test result.
