Inhibition of hypothalamic-pituitary-ovarian axis. IUD is an effective, simple and economical contraceptive tool. Its main contraceptive principles are as follows: it works through the local effect of foreign bodies; Foreign bodies stimulate the endometrium to produce non-bacterial inflammatory reaction, which is not conducive to embryo development; Mechanical action to prevent pregnant eggs from implantation; Stimulating the endometrium to produce prostaglandin affects the implantation of pregnant eggs. Hypothalamus-pituitary-ovarian axis has a secretory function and will not be affected by IUD. Therefore, it is wrong to inhibit the role of hypothalamus-pituitary-ovarian axis on the contraceptive principle of IUD. IUD is a kind of contraceptive device placed in uterine cavity. Because the devices used in the early stage are mostly annular, they are usually called IUD, also called intrauterine device, or IUD for short.