Freemartin placentation
Keywords: freemartins, bovine, slip, membrane, diagnosis, pregnancy, chorion, infertility, twins
This image of a 38 day twin bovine pregnancy shows the outer chorio-allantoic membrane and the two inner amnionic vesicles. Although the allantoic cavities remain separate (as show here; one stained with iodine and the other not stained) the chorionic membranes fuse early usually before this stage of gestation, allowing cell and hormonal exchange between the developing embryos. If one of the embryos is a female, it causes freemartinism in that embryo.
Image size: 1067 x 664 px
At approximately 28 to 30 days of gestation, the allantochorion membranes of most (not all) ruminant co-twins fuse, which causes vascular anastomoses to form between the two conceptuses. This results in freemartinism. Freemartinism is discussed in some detail elsewhere in LORI.
