Cervical flattening refers to the slow disappearance of the cervical canal as the uterus contracts regularly in late pregnancy before labor. The cervix gradually flattens from the original 3 centimeters, and after flattening, the mouth of the uterus slowly expands, at which time the flattened cervix becomes part of the soft birth canal, and when the mouth of the cervix expands to 10 centimeters, the head of the fetus slowly begins to descend, which is a normal physiological process in obstetrics. In mid-pregnancy, preterm labor also occurs when the cervix gradually shortens and then flattens out, and finally preterm labor occurs. After giving birth, the woman’s uterus slowly returns to the size she was when she was not pregnant through uterine contractions, and the cervix also returns to the length it was when she was not pregnant. It takes 42 days after delivery for the uterus to return to its original size, or a little longer if the uterus is not recovering properly.