Interactions of the trophoblast and maternal tissues in three closely related primate species.

The confluence of maternal and fetal tissues to form the placenta causes a wide variety of alterations in cells of both origins. Three closely related primate species were studied for similarities and differences in the interrelationships formed during various stages of placental development in the areas of implantation, decidualization, and trophoblastic involvement in the spiral arteries. Although certain similarities exist among the three species a surprising number of distinct differences were found to shed doubt on the common practice of assuming species-to-species similarity, particularly among primates.