Abstract:Objective: To evaluate effects of combined spinal and epidural anesthesia (CSEA) and nitrous oxide (N2O) inhalation used in labour analgesia. Methods: Ninety nulliparous women at term were randomly divided into three groups: study group Ⅰ, study group Ⅱ and control group. In the study two groups, CSEA and N2O inhalation were applied separately when cervix dilated 3 cm. Observed labour process, recorded analgesic effect, then drew maternal intravenous blood for β-EP determination. Results: The two study groups had a good effect on relieving labour pain, and the study group Ⅰ had better effect than the study group Ⅱ. In the study group Ⅰ, the active phase was shorter than that of the control group; and in the study group Ⅱ, the active phase, the second stage, the third stage and the total stage were all shorter than those of the control group. Between the study group Ⅰ and Ⅱ, there was no difference in labour duration. There was no difference about uterine contraction among the three groups, rate of spontaneous delivery, delivery forceps and cesarean section, postpartum hemorrhage volume, fetal distress and neonatal Apgar Scores. The concentration of β-EP in the three groups at delivery were all higher than those of postpartum. At delivery, the concentration of β-EP of the study group Ⅰ was the lowest; after delivery, the concentration of β-EP in the study group Ⅱ was the highest. Conclusions: CSEA and N2O inhalation can be applied in labour analgesia, relieving labour pain,decreasing labour duration, not influencing other labour factors. At delivery, the concentration of β-EP is sig nificantly increased, however decreased greatly after delivery, which indicated that β-EP took part in the labour analgesia.