Postovulatory predecidual development in the baboon, chimpanzee, and human

The development of predecidual tissue during the late postovulatory phase was evaluated by light microscopic study in the baboon, chimpanzee, and human being. While the predecidual cells of these species appeared to be similar morphologically, the degree of predecidual differentiation was greater in humans and chimpanzees than in baboons. The evidence indicated that the presence of a blastocyst was not required for decidualization to occur in these three primates. Further, decidualization was not dependent on coitus in chimpanzees and baboons, and was probably not essential in humans either.