What is the principle behind intrauterine device (IUD) insertion?

In daily life, there are numerous contraceptive methods available. For women who do not plan to become pregnant in the near term and cannot take oral contraceptives, intrauterine device (IUD) insertion—commonly referred to as “placing a ring”—is an option. But how does IUD insertion work?

How Does an IUD Work?

IUD insertion is a procedure in which a contraceptive device is placed inside the uterine cavity to prevent pregnancy. It operates primarily through two mechanisms: First, the presence of the IUD within the uterine cavity impedes sperm-egg interaction. After intercourse, sperm are unable to traverse the vagina and enter the uterine cavity, thereby preventing fertilization. Second, even if highly motile sperm manage to pass through the uterine cavity and reach the fallopian tubes to meet the egg, the resulting fertilized egg fails to migrate back into the uterine cavity and implant successfully—thus achieving contraception.

Implantation interference mainly slows down the nuclear translocation of estrogen receptors (ER) in endometrial cytoplasm, causing substantial ER accumulation in the cytoplasm. This triggers biological changes in the endometrium that hinder blastocyst implantation. Mechanical pressure exerted by the IUD induces endometrial tissue ischemia, stromal atrophy, glandular epithelial degeneration, and necrosis. In copper-containing IUDs, released copper ions penetrate cell nuclei and mitochondria, disrupting normal cellular metabolism.

After IUD insertion, many women experience mild lower abdominal discomfort and low-back pain. Adequate rest and keeping warm are recommended. We hope this explanation has been helpful!