It is widely agreed that epidural analgesia during labor is associated with an increased risk of operative delivery (forceps or cesarean section). However, many patients during labor will have confounding factors that predispose to both operative delivery and also to the patient receiving epidural analgesia. Such factors include dysfunctional labor requiring oxytocin augmentation, fetal malpresentation, large fetal size, presence of non-reassuring fetal heart rate patterns, or maternal exhaustion following long labor. Thus, it is crucial that such confounding variables be considered whenever the incidence of operative delivery is related to epidural analgesia. Retrospective studies usually fail to account for all confounding variables. Prospective, randomized trials are particularly difficult to perform, as random allocation of the method of pain relief is generally not well accepted.

Several recent studies have attempted to address this issue. In a prospective trial, Thorp et. al. (1) studied 93 women randomized to receive either epidural (n=48) or systemic narcotic analgesia (n=45). All subjects were healthy nulliparous women with a singleton fetus in spontaneous labor. The cesarean section rate (mostly for dystocia) was 2% in the narcotic group vs. 25% in the epidural group. The epidural group also had more requirement for oxytocin augmentation and a prolonged first and second stage of labor. However,
(a) dystocia was poorly defined,
(b) the station of fetal descent was never mentioned,
(c) the obstetricians were not blinded to the anesthetic management ,
(d) most epidurals were placed very early in labor, and
(e) the dose of oxytocin was relatively low.

In contrast, Chestnut (2, 3) randomized women to receive either early (<5 cm) or late (>5 cm) epidural analgesia. Separate analyses were performed for women in spontaneous labor and those receiving oxytocin augmentation. Neither study found a difference in operative delivery between early and late epidural administration. Important points here include:
(a) all patients had epidural analgesia (cf. Thorp's study (1) where a narcotic - only group was included),
(b) group separation was relatively unclear, i.e. "early" and "late" groups may have been actually quite similar, and
(c) the study may lack adequate power to support a finding of no difference between groups.

At present, the answer to this important question remains elusive. The obstetrical management of patients with epidural analgesia is likely to be an important determinant of mode of delivery (4). Even the individual obstetrician may be of importance in determination of outcome (5).

In summary, a recent American College of Obstetrics and Gynecology Committee opinion is relevant here: "Labor results in severe pain for many women. There is no other circumstance where it is considered acceptable for a person to experience severe pain, amenable to safe intervention, while under a physician's care. Maternal request is a sufficient justification for pain relief during labor" (6).

References:
1. Thorp JA, Hu DH, Albin RM, et. al. The effect of intrapartum epidural analgesia in nulliparous labor: A randomized, controlled, prospective study. Am J Ob Gyn 1993; 169: 851-8.

2. Chestnut 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.

3. Chestnut DH, Vincent RD, McGrath JM, et. al. Does early administration of epidural analgesia affect obstetric outcome in nulliparous women who are receiving oxytocin? Anesthesiology 1994; 80:1193-1200

4. Carli F, Creagh-Barry P, Gordon H. Does epidural analgesia influence the mode of delivery in primiparae managed actively? Int J Obstet Anesth 1993; 2: 15-20.

5. Goyert GL, Bottoms SF, Treadwell MC, Nehra PC. The physician factor in cesarean birth rates. N Engl J Med 1989; 320: 706-709.

6. American College of Obstetricians and Gynecologists: Committee opinion: Pain relief during labor. Number 118. 1993.