2Wong CA, Scavone BM, Peaceman AM, et al. The risk of cesarean delivery with neuraxial analgesia given early versus late in labor [J]. Obstet Gynecol Surv, 2005,60:424- 425.
2Alexander JM, Lucas MJ, Ramin SM, et al. The course of labor with and without epidural analgesia. Am J Obstet Gynecol, 1998, 178: 516-520.
3Sharma SK, Mclntire DD, Wiley J, et al. Labor analgesia and cesarean delivery: an individual patient meta-analysis of nulliparous women.Anesthesiology, 2004, 100: 142-148.
4Bailit JL, Dierker L, Blsnchard MH, et al. Outcomes of women presenting in active versus latent phase of spontaneous labor. Obstet Gynecol,2005, 105: 77-79.
5Chestnut DH, Mcgrath JM, Vincent RD, et al. Does early administration of epidural analgesia affect obstetric outcome in nulliparous women who are in spontaneous labor? Anesthesiology, 1994, 80: 1201-1208.
6Capogna G, Celleno D, Lyons G, et al. Minimum local analgesic concentration of extradural bupivacaine increases with progress of labour. Br J Anaesth, 1998, 80: 11-13.
7Palm S, Gertzen W, Ledowski T, et al. Minimum local analgesic dose of plain ropivaeaine vs. ropivaeaine combined with sufentanil during epidural analgesia for labour. Anaesthesia, 2001, 56: 526-529.
8Chen LK,Hsu HW, Lin C,J, et al. Effects of epidural fentanyl on labor pain during the early period of the first stage of induced labor in nulliparous women. J Formos Med Assoc, 2000, 99: 549-553.
9Rogers R, Gilson G, Kammerer Doak D. Epidural analgesia and active management of labor: effects on length of labor and mode of delivery.Obstet Gynecol, 1999, 93: 995-998.
10Ohel G, Harats H. Epidural anesthesia in early compared with advanced labor. Int J Gynaecol Obstet, 1994, 45: 217-219.