IUDs are not recommended during breastfeeding because of the relatively high failure rate. The uterus enlarges during pregnancy, and the size of the uterine cavity is slightly larger after delivery than during non-pregnancy, so the IUD may be displaced after it is placed in the uterine cavity, resulting in contraceptive failure. In addition, during breastfeeding, the hormone levels in the body have not returned to normal, and the uterus is softer, making it easier for complications to occur during the process of inserting the IUD, which may even lead to perforation of the uterus. Therefore, for safety reasons, it is not recommended to use the IUD during the breastfeeding period. It is recommended that the IUD be placed in the uterine cavity after the end of the breastfeeding period when menstruation has returned to normal, and that condoms be used as the main method of contraception during the breastfeeding period.