Pathology When does the Implantation occur? A On day 4 after feilization B After the endometrium undergoes a decidual reaction C When the embryo is at the morula stage D Only after priming of the uterine endometrium by progesterone and estrogen 💡 Explanation When does the Implantation occur? ✓ Correct Answer: D. Only after priming of the uterine endometrium by progesterone and estrogen