Some patients have this concern: Why is my endometrium sometimes B and sometimes C? Is C-shaped endometrium bad? Today, we will briefly explain the staging of the endometrium. The endometrium typing criteria under ultrasound follows the Gonen typing, which is divided into A, B and C types. Type A endometrium: It is also known as trilinear endometrium, with strong echogenic lines between the outer layer and the midline of the uterine cavity and hypoechoic or dark areas between the outer layer and the midline of the uterine cavity. This type is commonly seen in the early stages of endometrial hyperplasia. Type B endometrium: It is a homogeneous moderate intensity echogenic with intermittent strong echogenic midline in the uterine cavity. This type of endometrium is commonly seen in the late stage of endometrial hyperplasia. Type C endometrium: the endometrium is homogeneous and strongly echogenic with disappearance of the trilinear sign. This type of endometrium is commonly seen in the luteal phase. As can be seen, the endometrium varies with the menstrual cycle and is not static. the morphology of the endometrium under ultrasound is also related to the position of the uterus and the personal subjectivity of the physician. Clinically, we are more concerned with the thickness of the endometrium.