Britannica
Sources used in this answer
Where does a human blastocyst normally implant?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Fertilization
Fertilization occurs when a sperm cell penetrates and fuses with an egg (ovum).
A human blastocyst normally implants within the thickened lining of the uterus, known as the endometrium.12
Six to 10 days after fertilization, the blastocyst adheres to the uterine lining, which has been prepared by hormones to receive it. The blastocyst then erodes the superficial epithelium and embeds itself completely within the compact layer of the endometrium. This process allows the developing embryo to establish a physiological connection with the mother through the formation of the placenta.123
If a blastocyst implants outside the uterine cavity, the condition is referred to as an ectopic pregnancy, which is a serious medical concern.43