Terms like dichorionic or monochorionic are used to identify and describe the twins and refer specifically to the number of chorions, either two (one per baby) or one that is shared by both babies. (verywellfamily.com)
Subchorionic Hemorrhage (Hematoma): This happens when pockets of blood accumulate between the placenta and the uterus, in the folds of tissue called chorion. (momtricks.com)
By contrast, at d 34, 0.4 % and 2.1 % of genes were differentially expressed in chorion and allantois from clones, respectively (Fig. 2B and Table 1). (pnas.org)