To investigate and compare the effectiveness and influence among the methods of patient controlled epidural analgesia (PCEA), inhalation of nitrous oxide(N₂O) and drug analgesia.

To select Mar. 2004 to Oct. 2004 pregnant women 120 cases: the PCEA group, the nitrous oxide group, the drug analgesia group and the control group. The pregnant women of the PCEA group were injected fentanyl and ropivacaine in the epidural space. The nitrous oxide group were inhaled nitrous oxide (50%) premixed with oxygen (50%). The pregnant women of drug analgesia group were injected diazepam during latent phase and pethidine during active phase. The analgesia was not used in the control group. The degree of pain, duration of the labor, way of delivery, bleeding volume, rate of anoxia of newborn, blood gas analysis to maternal radius artery and fetal umbilical blood of 4 groups were observed.

The effect for analgesia labor of the PCEA group was much better than that of the nitrous oxide group and the drug analgesia group (χ²=119.888, P=0.000). There were no significant differences among 4 groups in the latent phase, the active phase, the second stage of labor, and the total stage of labor (P>0.100). The bleeding volume of 4 groups were alike to each other (P>0.100). The way of delivery has no significant difference among 4 groups(χ²=2.410, P=0.878). The blood analysis to maternal radius artery, fetal umbilical blood and the rate of anoxia of newborns of 4 groups revealed no significant differences(P>0.100).

The effectiveness of the PCEA for labor analgesia is confirmed and has rarely side-effect, and it can be the first choice. The inhalation of nitrous oxide and the drug analgesia also can safely provide effective labor analgesia.