23h 30min, jan 7, 2020 y - Implantation

Description:

Towards the end of the first week, the blastocyst embeds itself into the endometrium through the process of implantation. When this occurs, the superficial cells of the trophoblast fuse with each other to form a syncytiotrophoblast to secure the blastocyst to the uterine wall. The trophoblast secretes human chorionic gonadotropin (hCG) that directs the corpus luteum to survive, as well as continue to produce estrogen and progesterone. Pregnancy tests may be used at this point to check for hCG in urine.