Implantation

Implantation is a critical stage in pregnancy during which the embryo attaches to the wall of the uterus. This process begins approximately one week after fertilization and is completed over the course of several days.

Process of Implantation

The process of implantation begins when the blastocyst, a structure formed in the early development of mammals, reaches the uterus. The blastocyst then adheres to the uterine wall, a process known as apposition. Following apposition, the blastocyst embeds itself into the uterine wall, or endometrium, in a process known as invasion.

Factors Influencing Implantation

Several factors can influence the success of implantation. These include the health of the endometrium, the quality of the embryo, and the hormonal environment. Conditions such as endometriosis and polycystic ovary syndrome (PCOS) can negatively impact implantation.

Implantation and Pregnancy Tests

Implantation triggers the release of the hormone human chorionic gonadotropin (hCG), which is detected by pregnancy tests. Therefore, a pregnancy test may not show a positive result until after implantation has occurred.

Complications of Implantation

Complications can arise if implantation does not occur correctly. For example, an ectopic pregnancy occurs when the embryo implants outside the uterus, most commonly in the fallopian tube. This can be a life-threatening condition requiring immediate medical attention.

See Also

• Pregnancy
• Embryo
• Endometrium
• Ectopic pregnancy