1. Embryo implantation. The embryo develops for approximately 1 week after fertilization of the egg, forming a blastocyst at the time of implantation. The endometrium is invaded by trophoblast cells that surround the blastocyst. Once implantation has occurred, the decidual reaction transforms the entire uterine endometrium into the decidual membranes of pregnancy.
Source: Reproductive Physiology, Medical Physiology: The Big Picture
Citation: Kibble JD, Halsey CR. Medical Physiology: The Big Picture; 2015 Available at: Accessed: December 28, 2017
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