📖 Implantation

In Detail

Implantation is a critical step — about 50% of fertilized eggs fail to implant. The blastocyst 'hatches' from its protective zona pellucida and attaches to the endometrium in a process involving complex molecular signaling. Once implanted, the trophoblast cells begin producing hCG, which signals the corpus luteum to continue progesterone production. Implantation may cause light spotting (implantation bleeding) and mild cramping.