• Fangming Su, Xiaoping Wei, Xiaohe Chen, Zhiyang Hu, and Hongli Xu.
• Department of Obstetrics, Second People's Hospital Affiliated to Jinan University, Shenzhen 518020, China.
• Zhonghua Fu Chan Ke Za Zhi. 2002 Oct 1;37(10):584-7.

ObjectiveTo investigate the efficacy and safety of labor analgesia with inhalation of 50% nitrous oxide in oxygen.MethodsA total of 1300 cases of term primiparous women in labor were divided into two groups. Study group (n = 658) 50% nitrous oxide in oxygen was inhaled during labor for relieving labor pain. Control group (n = 642) intermittent inhalation of 50% oxygen was carried out during labor. Two groups were compared with following indices: duration of the labor, delivery mode, meconium stained of amniotic fluid, postpartum bleeding volume, neonatal Apgar score, side effect of nitrous oxide, and blood gas analysis of samples from maternal radius artery and fetal umbilical blood.ResultsThe efficiency of relieving labor pain in study group was much better than that of control group (80.9% vs 0.9%, P < 0.001). Rate of cesarean section in study group was lower than control group (11.6% vs 19.3%, P < 0.05). The active phase of labor in study group was shorter than control group (153 min vs 187 min, P < 0.05). There was side effect of dizziness in 39.4% cases of study group but there were no any complaint in the control group cases. There were no significantly differences in duration of the labor, meconium stained amniotic fluid, postpartum bleeding volume, neonatal Apgar score, and blood gas analysis between two groups (P > 0.05).ConclusionInhalation of 50% nitrous oxide in oxygen was safe and effective labor analgesia. It is acceptable. The measure of relieving labor pain may increase the vaginal birth rate. There is no severe side effect on mother and baby.

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