Endometrium generally refers to the lining of the uterus, and the thickness of the endometrium is usually more than 10 millimeters for menstruation, in addition, the thickness of the endometrium and menstruation at different times, is subject to regular changes. A woman’s endometrial lining thickness is going to change with the woman’s ovarian cycle. The endometrium will change accordingly during the proliferative phase, secretory phase, premenstrual phase and menstrual phase. Normal endometrial thickness varies at different times of the menstrual cycle, with the thickest endometrium usually around 10-12 millimeters. It usually does not exceed 12 millimeters before menstruation. Occasionally a little more than this is within the normal range and is not cause for alarm. Generally, the thickness of the endometrium is more than 10 millimeters can be menstruation, if abnormal menstruation is recommended to go to the hospital for examination, and follow the doctor’s instructions for treatment.