Abstract

Background

Labor pain is probably the most painful event in a woman's life. By the present consensus, epidural analgesia is the most effective and least depressive treatment for labor pain. Recent systematic reviews concluded that the risk of cesarean delivery or instrumental vaginal delivery for women receiving early epidural analgesia has not increased. However, studies designed for discussing this topic in Taiwan are few. In this study, the association of the intervention timing with labor outcomes in nulliparous women in Taiwan is discussed.

Methods

We performed a retrospective chart review in parturients who underwent epidural analgesia for labor pain. Only nulliparae were included and divided into four groups based on the cervical dilatation width of 1, 2, 3, and 4 cm when they underwent epidural analgesia. We retrieved each patient's demographic characteristics, the course of labor and delivery, and the management of epidural analgesia from the medical chart.

Results

A total of 799 nulliparae was included. The numbers of parturients with cervical dilatation width of 1, 2, 3, and 4 cm were 119, 338, 258, and 84 respectively. There was no significant difference in demographic factors, regimen of epidural analgesia, loading volume, and anesthesiologist in charge among the four groups. The percentages of cesarean delivery in the four groups were 27.73%, 20.71%, 15.89%, and 20.24%, respectively, and there was no significant difference among these four groups (p = 0.0651). The incidences of instrumental delivery in four groups were 13.51%, 14.59%, 18.65%, and 21.43% respectively, and there was no significant difference among these four groups either (p = 0.2278).

Conclusion

Our results revealed that the timing of epidural intervention affects neither the cesarean delivery rate nor the instrumental delivery rate on nulliparae in Taiwan with the cervical dilatation width ranging from 1 cm to 4 cm. The fear of increasing cesarean section rate after early epidural analgesia is unfounded. Women in labor can choose pain relief at any time.

Keywords

analgesia, epidural; anesthetics, local: ropivacaine; cesarean section; labor pain;

1. Introduction

Labor pain is probably the most painful event in a woman's life.¹ By the present consensus, neuraxial analgesia techniques, including epidural, spinal, and combined spinal-epidural approaches are the most effective and least depressant treatments for labor pain.² Nevertheless, the previous studies disclosed the increased the cesarean delivery rate in parturients who received epidural analgesia in the early labor stage.3, 4, 5, 6 Thus, the American College of Obstetricians and Gynecologists (ACOG) Task Force in 2000 recommended that obstetric practitioners should delay the administration of epidural anesthesia in nulliparous women until the cervical dilatation reaches at least 4–5 cm.⁷ However, recent randomized control trials showed no difference in the incidence of cesarean delivery between the early and late groups.8, 9, 10, 11The ACOG committee opinion in 2006, recommended that “The fear of unnecessary cesarean delivery should not influence the method of pain relief that women wish to choose during labor.”¹² These recommendations revealed that the fear of increasing cesarean section rate still exists in the minds of many physicians and parturients, especially with the administration of epidural analgesia in early labor course. Besides, the definition of “early” epidural analgesia varies in different studies, with cervical dilatations ranging from 2 cm, 3 cm, 4 cm to 5 cm.4, 5, 6

Studies designed for discussing this topic in Taiwan are few. Thus, in this study, the association of the timing of the epidural analgesic intervention with labor outcomes in nulliparous women in Taiwan was discussed. In our study, the parturients were not divided into early or late epidural analgesia groups but by a clear-cut cervical dilatation instead. The parturients were divided into four groups according to their cervical dilatation width (cm) while receiving epidural analgesia.

2. Methods

This study was approved by the Ethics Committee of our hospital. A retrospective chart review of parturients who underwent epidural analgesia for labor pain in a teaching hospital in Taipei City from January 2005 to December 2006 was conducted.

The epidural analgesia was initiated at parturient's request by the anesthesiologist on duty if there were no contraindications, such as infection at the site of injection, coagulopathy or anticoagulant medication, preexisting neurological deficits, hypovolemic shock, and severe heart disease.

After the skin was infiltrated with 1% xylocaine, an epidural catheter (Portex Epidural Minipack) was inserted via L3-4 or L4-5 intervertebral space through a 16- or 18-gauge Tuohy needle in place with the parturient in the lateral position. The “loss of resistance technique” was used to identify the epidural space. The catheter was threaded 4–7 cm cephalad through the needle. Then, testing with 1% xylocaine was done to rule out intrathecal or intravascular catheterization before the catheter was secured. A bolus dose of 1% xylocaine or 0.2% bupivacaine or 0.17% ropivacaine was given epidurally with or without fentanyl 50 μg. Then, 0.1% ropivacaine with fentanyl 2 μg/mL was infused continuously at a rate of 8-15 mL/hour. The verbal numeric rating scale (NRS) of pain was recorded by a nurse anesthetist immediately before administrating the epidural anesthetic, 30 minutes after epidural analgesia, and at any time when the patient complained of pain. Maternal satisfaction of painless labor was also evaluated on the first postpartum day. All the procedures of analgesia and evaluation were standardized and recorded on the medical chart of each parturient.

All nulliparae who received epidural analgesia during January 2005 to December 2006 were included. Then, we excluded those who had incomplete chart records, had abortion or intrauterine death, saw repeat epidural catheterization at any time during the labor course, had unintentional intrathecal catheterization, did not use ropivacaine in subsequent continuous infusion, or received epidural analgesia while the cervical dilatation width was 0 cm or more than 5 cm.

Eligible nulliparae were divided into four groups on the basis of the cervical dilatation width at the time of epidural analgesic intervention. We retrieved each nullipara's demographic characteristics, the course of labor and delivery, and the management of epidural analgesia from medical chart. All data were analyzed with one-way analysis of variance (ANOVA) for continuous variables and Chi-square test or Fisher's exact test for categorical variables. A pvalue < 0.05 was considered statistically significant. All statistical analyses were performed using SPSS 15.0 (SPSS, Inc., Chicago, IL, USA).

3. Results

There was a total of 5809 parturients admitted in our hospital from January 2005 to December 2006, among whom 1015 parturients (17.47%) received epidural analgesia. We excluded 216 parturients of whom 136 were multiparae, three had incomplete chart records, two had intrauterine death, nine had reported epidural catheterization, 22 did not use ropivacaine in the subsequent continuous infusion, 10 had an initial cervical width of 0 cm, 25 had an initial cervical width of 5 cm, and nine had an initial cervical width of 6 cm.

A total of 799 nulliparae was included and divided into four groups according to the cervical widths 1 cm, 2 cm, 3 cm and 4 cm, at the time of epidural analgesic intervention. The numbers of parturients in four groups were 119, 338, 258, and 84 respectively. The demographic data of parturients and newborns, including maternal age, maternal weight, maternal height, newborn gestational age, newborn weight, newborn height, and newborn sex, did not differ significantly in the four groups. The factors associated with epidural analgesia, such as loading drugs, loading volume, and performers, were not significantly different among the four groups (Table 1). The cesarean delivery rate in four groups was 27.73% (33/119), 20.71% (70/338), 15.89% (41/258), and 20.24% (17/84). The rate of instrumental delivery was 13.51% (16/119), 14.59% (49/338), 18.65% (48/258), and 21.43% (19/84). No significant difference was observed among the four groups in the cesarean delivery rate (p = 0.0651, Chi-square test) and the instrumental delivery rate (p = 0.2278, Chi-square test, 7 parturients have missing values).

Table 1. Demographic data of mother-, newborn-, and analgesia-associated factors. Data are presented as mean ± SD or percentage.

Download full-size image

The other minor outcomes, such as Apgar score, NRS, and parturients' satisfaction, were also not significantly different in the four groups as shown in Table 2. The significant difference among the four groups was the use of meperidine. The percentage of meperidine use before the parturients requested for epidural analgesia was 9.4%, 16.51%, 17.23%, and 26.84% (p = 0.0144, Chi-square test).

Table 2. Labor outcome. Data are presented as mean ± SD or percentage.

Download full-size image

4. Discussion

There were three major findings in this study. First, the timing of epidural analgesia in nulliparae was not associated with the cesarean section rate. Second, the duration of the second stage and the instrumental delivery rate were irrelevant to the timing of initiating epidural analgesia. Finally, the rate of meperidine use before epidural analgesia was higher in the later group.

4.1. The effect of neuraxial anesthesia on cesarean section rate

The worry about increasing the cesarean delivery rate during the early administration of epidural analgesia for labor pain was based on the findings of retrospective studies and secondary analysis of prospective studies that were not primarily designed to answer this specific question.³ Results of these studies concluded that early epidural analgesia could be associated with a higher rate of cesarean delivery.4, 6 Hui-Ling Lee et al conducted a retrospective chart review of the clinical events in nulliparae of Taiwan who received epidural analgesia in 2008. They found that early epidural analgesia would lead to a significantly higher rate of cesarean section than would late epidural analgesia.⁶ However, recent systemic review and randomized control trial have shown no difference in the rate of cesarean delivery between groups receiving early and late epidural analgesia.8, 9, 10, 11 Our result was also in accord with the recent publications. Even our study subdivided the intervention timing and attempted to determine the accurate “safe” timing to start the epidural analgesia; our result supported the theory that there was no association between the timing and the cesarean delivery rate. The fear of increasing cesarean section rate after early epidural analgesia is unnecessary.

4.2. The effect of neuraxial anesthesia on instrumental vaginal delivery rate and the duration of second stage of labor

Observational data suggest an association between neuraxial labor analgesia and instrumental vaginal delivery. Interpretation of these data is difficult because of the presence of multiple confounding factors, such as maternal pain and the urge to bear down, neuraxial analgesia-induced motor blockade, and position of the fetal vertex and station.¹³ The contribution and interaction of these factors to the vaginal delivery are not only poorly understood, but also had not been well controlled in many studies. These confounding factors resulted in conflicting findings in different studies. Many impact studies14, 15 have not shown a difference in the instrumental vaginal delivery rate before and after the availability of neuraxial analgesia and were confirmed by a systematic review of seven impact studies involving more than 28,000 parturients.¹⁶ In contrast, the systematic reviews of randomized controlled trials of neuraxial analgesia as compared with systemic opioids analgesia have concluded that neuraxial analgesia is associated with an increased risk of instrumental vaginal delivery.¹⁷

One of the confounding factors is the concentration of neuraxial analgesics during the second stage of labor. Epidural local anesthetic would relax the abdominal wall musculature and then result in decreased effectiveness of maternal expulsive efforts. Besides, severe sensory blockade of the birth canal might also decrease the maternal ability to coordinate expulsive efforts with uterine contractions. Additionally, the relaxed pelvic floor musculature may interfere with fetal rotation during descent.¹³ All these may also result in a prolonged duration of the secondary stage of labor.

Factors influencing the progress of labor are hitherto not well understood. It is widely agreed previously that effective neuraxial analgesia prolongs the second stage of labor.¹³ However, this viewpoint was based on the trials of epidural analgesia with 0.25% bupivacaine, a much higher dose than the current norm. Indeed, several groups of investigators have demonstrated that neuraxial analgesia with this technique results in a higher instrumental vaginal delivery rate as compared with the low-dose bupivacaine-opioid technique via combined spinal and epidural anesthesia (CSE) with 0.0625% bupivacaine plus 2 μg of fentanyl.18, 19 The increased instrumental vaginal delivery rate may have partly resulted from the motor and sensory block. However, recent studies including the systemic review of randomized controlled trials concluded that the early administration of neuraxial analgesia neither increases the instrumental vaginal delivery rate8, 9, 10, 11nor increases the incidence of prolonged labor. 11, 20, 21 Our data agreed with this finding and the results of the study conducted by Hui-Ling Lee et al in Taiwan.⁶ We conclude that our regimen with 0.1% ropivacaine plus fentanyl 2 μg/mL neither leads to motor blockade nor increases the length of the second stage of labor and the rate of the instrumental vaginal delivery rate.

4.3. Meperidine use before epidural analgesia

Previous studies disclosed that the mean intensity of labor pain increases with wider cervical dilatation and is closely correlative with the intensity, duration, and frequency of uterine contraction.²² As we would expect, there was significant increase in meperidine use before the parturients asked for epidural analgesia in later epidural analgesia groups. Nevertheless, nausea, vomiting, and sedation were common maternal side effects of systemic opioid. Besides, respiratory depression was the major neonatal concern.²³Thus, we suggest that the parturient's request is a sufficient indication to perform epidural analgesia to prevent unnecessary suffering from labor pain and prevent the systemic opioid use.

The prevalence of epidural painless labor in this study was 17.47%, which was considerably lower than many developed countries such as the United States and the European Union, where the prevalence ranged between 23.6% and 78%.24, 25, 26 Our result does not represent the prevalence in the whole of Taiwan. However, we believe that the prevalence in the rural areas of Taiwan is lower than what we had seen because of the insufficient number of anesthesiologists in the rural area. Factors influencing parturients' decision of accepting epidural painless labor included the education level, the fear of the needle, fever of complications and side effects, connotative of prolongation of labor, and the increased cesarean delivery rate.²⁷ The results of this study disclosed that there was no so-called “proper” timing to prevent unnecessary cesarean delivery and no reason to delay the epidural analgesia. The fear of increasing cesarean section rate after early epidural analgesia is unnecessary. Women in labor can choose pain relief at any time.

This study had some limitations. First, oxytocin usage was not recorded; therefore, we could not recognize its effect on the labor course and the association with the mode of delivery. Second, most of our parturients accepted epidural analgesia when their cervical dilatation was 1-4 cm. There was large discrepancy in sample size between our study groups and the groups with cervical dilatation widths of 0 cm, 5 cm, and 6 cm. To prevent the bias of small sample, we excluded the latter. Third, our regimen of bolus dose of epidural analgesia is not unified. A prospective study with adequate control on potential confounders should be designed for future study.

Acknowledgments

This study was supported by a grant from Fu Jen Catholic University (FJU-409631030417).