Some women will experience stomach pain after placing the IUD, which is considered to be caused by inflammatory reaction, inappropriate size of the IUD, and stress reaction. 1. Inflammatory reaction stimulation: after placing the IUD, women have sex or take a sitz bath too soon, which, coupled with their weak physical condition, can easily cause pathogenic bacterial infection and lead to the emergence of pelvic inflammatory disease, which leads to stomach pain, increased vaginal discharge and other uncomfortable symptoms. 2. Inappropriate size of birth control ring: If the size of the birth control ring placed by the patient is inappropriate, it can also lead to contraction of the uterus, thus resulting in stomach pain. Especially if the IUD is too big and the uterine cavity is small, it can stimulate the uterus to contract and cause stomach pain. 3. Stress response: When the IUD is placed, resulting in a sudden change in the intrauterine environment, the endometrium and myometrium can experience a stress response, which can cause irregular shedding of the endometrium and irregular contractions of the uterus, resulting in a small amount of vaginal bleeding and stomach pain. Therefore, if you experience stomach pain after placing a birth control ring, it is recommended that you go to the hospital in time and have reasonable treatment under the guidance of your doctor.