Implantation and HCG

Script: After traveling down the uterine tube, the early embryo embeds itself into the inner wall of the mother's uterus. This process, called implantation, begins 6 days and ends 10 to 12 days after fertilization.

Cells from the growing embryo begin to produce a hormone called human chorionic gonadotropin, or hCG, the substance detected by most pregnancy tests.