Under normal circumstances, the thickness of the endometrium changes with the menstrual cycle, before menstruation the endometrium reaches the thickest degree, normally around 1.2cm, due to individual differences, some people may be slightly thicker, some people will be slightly thinner, are all normal phenomena. After menstruation, the thickness of the endometrium is relatively thin, around 5-6mm. As the proliferative phase progresses towards ovulation, the thickness of the endometrium gradually increases, and during ovulation the thickness of the endometrium should reach at least 9mm, which is conducive to the implantation of the fertilized egg. In addition, not only should we observe the thickness of the endometrium, but also observe whether the endometrium echoes are uniform, whether the thickness is uniform, so that we can distinguish whether there is endometrial pathology or inflammation, which is conducive to providing further clinical diagnosis.