Circumvallete Placenta

In extrachorial placentas, the edge of the placenta is uncovered except for some fibrin since the chorion laeve inserts at some distance inside rather than the rim of the placenta. There are two morphologic forms of extrachorial placentas. 1) Circumvallete (shown here) : the marginal membrane is rolled up and folded back on itself; 2) Circummarginate : the transition from membranous to villous chorion is flat. This form is clinically insignificant; however, the circumvallete placenta is associated with threatened abortion, membrane rupture, and antepartum hemorrhage. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission