Definition: Abnormalities of the birth canal include abnormalities of the bone birth canal and abnormalities of the soft birth canal. Abnormalities of the skeletal birth canal include entrance (planar) stenosis (mainly the entrance anteroposterior diameter narrow, mainly to measure the diagonal diameter), middle pelvic stenosis (mainly to measure the ischial interspinous diameter), outlet stenosis (to measure the ischial internodal diameter And ischial tuberosity diameter + sagittal diameter after exit mainly). According to the above diameters, the three levels of pelvic stenosis are divided into critical level 1, relative level 2 and absolute level 3, which are three degrees. The soft birth canal includes the soft tissues of the lower uterus, cervix, vagina and pelvic floor. Its abnormalities can be caused by congenital dysplasia and acquired diseases, including vaginal septum, mediastinum, masses, cervical adhesions (scars), toughness, edema, cancer, and deformities Or scarred uterus, uterine fibroids and ovarian tumors, etc. In most cases, the birth canal is abnormal and the pregnancy ends with a cesarean section.
Definition: The passage through which the fetus is delivered from the mother, including the bone birth canal and soft birth canal. The bone birth canal is the real pelvis, and its size and shape are closely related to childbirth. Three (imaginary) planes of the pelvis: entrance, middle pelvis and exit. The three diameters of the entrance are more important: the front and back diameter is 11 cm, and the basin is closely related to this line; the horizontal diameter is 13 cm; the oblique diameter is 12.75 cm. A diameter of the middle pelvis is very important: the transverse diameter of the middle pelvis (diameter between the ischial spines) is 10 cm, which is closely related to internal rotation. The three diameters of the pelvic outlet are very important: the transverse diameter of the outlet (diameter between the ischial tuberosity) 9 cm; the anteroposterior diameter of the outlet (the distance from the lower edge of the pubic symphysis to the sacrococcygeal joint) 11.5 cm; the posterior sagittal diameter (the sacrococcygeal joint to the ischium) The distance between the midpoint of the nodule line) is 8.5 cm. If the exit transverse diameter is short, but the exit transverse diameter plus posterior sagittal diameter> 15 cm, the fetus (only medium size or lower weight) can be delivered by the posterior triangle. Pelvic axis and pelvic slope: the curve connecting the midpoints of the three imaginary planes of the pelvis is the pelvic axis, downwards backwards/downwards/downwards forwards; when women stand upright, the angle between the pelvic entrance plane and the ground plane is the pelvis Slope. It is generally 60°. The angle is too large to affect the tyre head connection.