Labor and delivery is a unique physiological experience of women. Inappropriate length of labor progress during vaginal delivery may produce great risks for mother and fetus. Especially the slow progress is one of the most important reasons for the occurrence of cesarean section during vaginal delivery, which still with a high incidence in recent years.Previous studies have found that there was a significant correlation between the genetic polymorphisms of β 2-adrenergic receptor (β2AR) and the duration of vaginal delivery.Therefore, the researchers intend to investigate the distribution of β2-adrenergic receptor (β2AR) genetic polymorphisms among Chinese parturient and observe the relationship between the genetic polymorphisms and labor process after labor analgesia.