Endometrial thickness can usually be observed by ultrasound or MRI to clarify the presence of any abnormalities. Ultrasound is a non-invasive, convenient and easily accepted test that can reveal endometrial thickening or uneven echogenicity of the endometrium, which can be followed by laparoscopy in case of abnormalities. The endometrium can be examined by MRI and can be seen in sagittal position showing pockets of uniform high signal, yielding the thickness of the endometrium. Endometrial thickness has different standard values in different menstrual cycles. In the first half of the menstrual cycle, the endometrium is thin and may be 3-5 mm thick, while in the second half of the menstrual cycle, the endometrium is thicker and may be about 10 mm thick. In the case of menopausal women, the thickness of the endometrium is usually no more than 5 mm. observing the endometrium just after menstruation, it is clearer whether there is abnormal hyperplasia, etc. Endometrial lesions are an important cause of abnormal endometrial thickening, including simple hyperplasia, complex hyperplasia, atypical hyperplasia, and endometrial cancer, etc. Pathological tests can be performed, and if the results are not abnormal, long-term follow-up observation is possible. If abnormal hyperplasia is found, progesterone can be given or surgical treatment can be performed depending on the case. Observation during ovulation can clarify whether there is excessive thinning of the endometrium and whether it affects conception, so the observation time can be chosen according to the specific situation.