There are several reasons for postpartum depression in women: first, endocrine factors. During the process of pregnancy and delivery, the endocrine environment in the body produces great changes, especially within 24 hours after delivery, the rapid change of hormone level in the body is the key to the occurrence of postpartum depression. It is found that the release of placental steroids reaches the highest value before delivery, and patients show happy mood; when placental steroids suddenly decrease after delivery, patients will show depression. Second, genetic factors. The incidence of postpartum depression is higher in mothers with family history of mental illness, especially those with family history of depression. Third, obstetric factors. The prenatal state of mind is related to the onset of postpartum depression. Complications during and after delivery, such as obstructed labor, assisted delivery using assisted reproductive technology, long duration of the first stage of labor and vaginal assisted delivery surgery, can bring tension and fear to the mother, leading to enhanced physiological and psychological stress and inducing postpartum depression.