The uterus is located in the middle of the pelvis, with the bladder in front and the rectum behind. The position of the uterus is classified as anterior, flat and posterior. The flat position of the uterus is a description of the position of the uterus in the uterine cavity and is a normal uterine position that does not require special intervention. The flat position of the uterus is inverted pear-shaped, well-defined and smooth. In some people, the uterus is in a flat position, also known as intermediate uterus, with a longitudinal section that is horizontal to the uterus and an angle of 180° between the uterine body and the cervix. In the transverse section, the uterine fundus is triangular, the uterine body is oval, and the central part is strongly echogenic, which is seen between the anterior and posterior positions and is a normal uterine position. Most women have an anterior uterus and are more likely to conceive. A relatively abnormal uterine position is the posterior uterus, which has an oblique inverted pear shape. Most posterior uteruses do not cause abnormalities, but sometimes a more severe posterior position of the uterus can interfere with the discharge of menstrual blood, often leading to menstrual pain. The obstruction of menstrual blood discharge increases the pressure in the uterine cavity and can lead to backflow of menstrual blood into the pelvis, where the endometrium is planted on the surface of the ovaries or on the surface of the pelvic peritoneum, which can form endometriosis and should be guarded against.