IUDs do not cause polycystic ovary syndrome, the cause of which is still unknown. The side effects of IUD insertion into the uterine cavity are as follows: 1) irregular vaginal bleeding; 2) inflammation; 3) possible displacement of the IUD or its removal. The contraceptive mechanism of the IUD into the uterine cavity is mainly the formation of sterile inflammation in the uterus, thus preventing the fertilized egg from being laid and achieving the purpose of contraception. Polycystic ovaries are non-ovulatory or sporadic ovulation, with polycystic changes in the ovaries bilaterally, and have nothing to do with the IUD being inserted into the uterine cavity. If polycystic ovary syndrome is detected, systematic clinical treatment is given.