Condition analysis: The endometrium changes periodically according to the periodic secretion of ovarian hormones throughout the menstrual cycle. The reason of endometrial thickening is mainly due to the excessive stimulation of estrogen on endometrium. 1. Menstrual period: The functional layer of endometrium falls off and the basal layer remains. 2. Proliferative stage: the endometrial thickness reaches1-3 mm on the 6th-14th day of menstruation; Secretion period: the thickness of endometrium reaches 5-7 mm on the 6th-15th-28th day of menstruation. Suggestion: menstrual cycle is the main factor. If you have uterine fibroids, it depends on the size of the specific fibroids. If it generally does not cause symptoms, you can check it regularly and follow it up for 3 months!