Endometrial cups
Keywords: equine, pregnancy, eCG, cups
Endometrial cups, eCG and infertility
At about 28 to 35 days of gestation, cells from the embryo invade the endometrium, forming endometrial cups. It is not clear why they were named as such, perhaps because they have a cupped appearance when cut in cross-section. These structures are a source of equine chorionic gonadotropin (eCG) and are shown here, adjacent to a healthy embryo at about 38 days of gestation. The cups are indicated by green arrows.
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As shown elsewhere, endometrial cups are associated with secondary (accessory) ovulations during pregnancy but the exact relationship between endometrial cups and secondary corpora lutea remains an enigma.
Endometrial cups are rejected by the immune system of the dam at variable stages of pregnancy but usually eCG concentrations reach baseline by about 120 to 150 days of gestation. In unusual cases, they can persist throughout pregnancy.
