The contraceptive principle of the IUD is that the endometrium is stimulated by a foreign body for a long time, causing a sterile inflammatory reaction, which clinically prevents the fertilized egg from being laid, thus achieving the purpose of contraception. In addition, the foreign body reaction of the IUD can also damage the endometrium and produce prostaglandins, which in turn can change the peristalsis of the fallopian tubes and cause the fertilized egg to run out of sync with the endometrium, thus affecting the fertilized egg’s implantation. In addition, the birth control ring containing progesterone mainly releases a large amount of progesterone, causing the endometrial glands to atrophy, which can also be clinically detrimental to the fertilization of the egg to achieve the purpose of contraception. The contraceptive effect of IUD is very good, some IUDs can achieve 99.5% contraceptive effect.