Endometrial thickness of 15mm caused by physiological reasons is not dangerous, such as pregnancy, pathological causes may be dangerous, such as endometrial polyps, endometrial cancer, the degree of danger varies from person to person. 1. During a menstrual cycle, the thickness of endometrial lining varies. The endometrial lining is relatively thin when the menstruation is just clean and the thickness is about 6~7mm, the endometrial lining is about 9mm thick during the ovulation period, which is conducive to the implantation of fertilized egg, and the endometrial lining is relatively thick during the premenstrual period, with the thickness of 10-12mm or 13mm, which is a normal phenomenon. 2. With the increase of hormone level in the body after pregnancy, the endometrium will also gradually thicken, after pregnancy, the endometrium can be thickened to more than 15mm, the thickening of the ecdysis to form a package of ecdysis, the bottom of the ecdysis, true ecdysis, in this case it is normal, there is no danger. 3. without pregnancy in the case of menstruation just clean or ovulation endometrial thickness of 15mm is not normal, there may be a lot of vaginal bleeding, bleeding time prolonged performance, not timely treatment is easy to anemia, low blood pressure, shock, there will be a certain degree of danger. 4. Postmenopausal women with endometrial thickness of 5mm or less, endometrial thickening of 15mm may be caused by endometrial polyps, endometrial cancer, caused by different causes, the degree of harm to the body is also different. It is necessary to carry out hysteroscopy or diagnostic scraping, and the tissues are sent to the pathology examination, which can clarify the diagnosis. If the endometrium is 15mm thick with abnormal vaginal bleeding, you should go to the hospital for examination to determine the cause.