The pelvic tilt is measured by 1) the angle formed by the pelvic inlet plane and the ground plane in the upright position; 2) the angle formed by the pelvic inlet plane and the vertical plane when lying down. The pelvic obliquity is 50-55 degrees in non-pregnancy and can increase by 3-5 degrees in late pregnancy. Under normal circumstances, pelvic tilt between 60-70 degrees does not affect delivery. If the pelvic tilt is greater than or equal to 70 degrees, it is called excessive pelvic tilt. In this case, the sacrum is often forward and upward, while the pubic arch is displaced backward and downward, which hinders the articulation, descent and internal rotation of the fetal head, and often requires cesarean section to terminate the pregnancy.