If the uterine lining is 18mm thick and you have not yet had your period, it is first recommended to rule out the possibility of pregnancy. If there is no pregnancy, you can take oral progesterone gelatin pills to induce menstruation, take two pills once a day for 3 days, and menstruation will come in 3-7 days after stopping the pills. As the endometrium is thicker, the menstrual flow will be relatively larger, so there is no need to be nervous; however, if it is more than 80ml, it is recommended to go to the hospital to stop the bleeding and have a repeat ultrasound examination after the menstrual period is cleared. If the endometrium is still in a thick state, it is recommended to go to the hospital for diagnostic scraping between 6-12 hours after the next menstrual period and send the scraped out endometrium to the pathology laboratory for further treatment according to the result.