The process of delivery refers to the whole process that the fetal presenting part passively performs a series of adaptive rotations to adapt to the different shapes of pelvic planes when passing through the birth canal, and passes through the birth canal with its smallest diameter line. Clinically, the left anterior position of occipital presentation is the most common, including joint, descent, flexion, internal rotation, extension, reduction and external rotation, fetal shoulder and fetal delivery. The delivery process is actually a continuous movement, 1. convergence, the biparietal diameter of the fetal head enters the pelvic entrance plane, and the lowest point of the skull approaches or reaches the level of the sciatic spine, which is called convergence; 2. Descending, the movement of the fetal head along the pelvic axis is called descending, which runs through the whole process of delivery; 3. Protrusion is conducive to the continued decline of the fetal head; 4. Internal rotation: the fetal head completes internal rotation at the end of the first stage of labor; 5. Upward extension, when the fetal head completes internal rotation, the prostrate fetal head has reached the vaginal opening, and gradually extends upward, and the fetal head is delivered; 6. Reset and external rotation: after the fetal head is delivered, the fetal head and the shoulder are reset to normal anatomical relationship, and then rotated externally to maintain the vertical relationship between the fetal head and the shoulder; 7. Shoulder and fetus are delivered, and the whole delivery process is completed.