Labour analgesia and obstetric outcomes
2010; Elsevier BV; Volume: 105; Linguagem: Inglês
10.1093/bja/aeq311
ISSN1471-6771
AutoresChristopher Cambic, Cynthia A. Wong,
Tópico(s)Nausea and vomiting management
ResumoSummaryNeuraxial analgesic techniques are the gold standards for pain relief during labour and delivery. Despite the increased use and known benefits of neuraxial labour analgesia, there has been significant controversy regarding the impact of neuraxial analgesia on labour outcomes. Review of the evidence suggests that effective neuraxial labour analgesia does not increase the rate of Caesarean delivery, even when administered early in the course of labour; however, its use is associated with a prolonged second stage of labour. Effective second-stage analgesia might also be associated with an increased rate of instrumental vaginal delivery. Neuraxial analgesic techniques are the gold standards for pain relief during labour and delivery. Despite the increased use and known benefits of neuraxial labour analgesia, there has been significant controversy regarding the impact of neuraxial analgesia on labour outcomes. Review of the evidence suggests that effective neuraxial labour analgesia does not increase the rate of Caesarean delivery, even when administered early in the course of labour; however, its use is associated with a prolonged second stage of labour. Effective second-stage analgesia might also be associated with an increased rate of instrumental vaginal delivery. Key points•The effects of neuraxial labour analgesia on the progress of labour and labour outcomes have generated considerable controversy.•The evidence indicates that effective labour analgesia does not increase the rate of Caesarean delivery.•Effective labour analgesia can prolong the second stage of labour, and might also increase the rate of instrumental vaginal delivery.•The potential benefits and risks of neuraxial labour analgesia must be tailored to the needs of each parturient. •The effects of neuraxial labour analgesia on the progress of labour and labour outcomes have generated considerable controversy.•The evidence indicates that effective labour analgesia does not increase the rate of Caesarean delivery.•Effective labour analgesia can prolong the second stage of labour, and might also increase the rate of instrumental vaginal delivery.•The potential benefits and risks of neuraxial labour analgesia must be tailored to the needs of each parturient. Neuraxial techniques are the gold standard for intrapartum labour analgesia. Multiple randomized controlled trials comparing epidural analgesia with systemic opioids, nitrous oxide, or both have demonstrated lower maternal pain scores and higher maternal satisfaction with neuraxial analgesia.1Anim-Somuah M Smyth R Howell C Epidural versus non-epidural or no analgesia in labour.Cochrane Database Syst Rev. 2005; 4: CD000331PubMed Google Scholar, 2Howell CJ Chalmers I A review of prospectively controlled comparisons of epidural with non-epidural forms of pain relief during labour.Int J Obstet Anesth. 1992; 1: 93-110Abstract Full Text PDF PubMed Scopus (56) Google Scholar, 3Paech MJ The King Edward Memorial Hospital 1,000 mother survey of methods of pain relief in labour.Anaesth Intens Care. 1991; 19: 393-399PubMed Google Scholar, 4Ramin SM Gambling DR Lucas MJ Sharma SK Sidawi JE Leveno KJ Randomized trial of epidural versus intravenous analgesia during labor.Obstet Gynecol. 1995; 86: 783-789Crossref PubMed Scopus (285) Google Scholar In addition to their analgesic benefits, the physiological benefits of neuraxial analgesia for the mother and fetus are well-documented: neuraxial analgesia has been shown to improve maternal cardiovascular and pulmonary physiology, and the acid–base status of the fetus.5Jouppila R Hollmen A The effect of segmental epidural analgesia on maternal and foetal acid-base balance, lactate, serum potassium and creatine phosphokinase during labour.Acta Anaesth Scand. 1976; 20: 259-268Crossref PubMed Scopus (48) Google Scholar, 6Lederman RP Lederman E Work B McCann DS Anxiety and epinephrine in multiparous labor: relationship to duration of labor and fetal heart rate pattern.Am J Obstet Gynecol. 1985; 153: 870-877Abstract Full Text PDF PubMed Scopus (118) Google Scholar, 7Levinson G Shnider SM deLorimier AA Steffenson JL Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid-base status.Anesthesiology. 1974; 40: 340-347Crossref PubMed Scopus (142) Google Scholar, 8Shnider SM Abboud T Artal R Henriksen EH Stefani SJ Levinson G Maternal catecholamines decrease during labor after lumbar epidural analgesia.Am J Obstet Gynecol. 1983; 147: 13-15Abstract Full Text PDF PubMed Scopus (150) Google Scholar As a result of the superior analgesia and maternal–fetal benefits afforded by neuraxial techniques, and their improved safety, use of neuraxial labour analgesia has progressively increased over the past three decades. In the USA, the percentage of parturients receiving neuraxial analgesia for labour rose to 77% in 2001 from 21% in 1981; in the UK, a little over 33% of parturients chose neuraxial analgesia for childbirth in 2008–09.9National Health Service. Maternity Statistics 2008–09 http://www.ic.nhs.uk/statistics-and-data-collections/hospital-care/maternity/nhs-maternity-statistics-2008-09Google Scholar 10Bucklin BA Hawkins JL Anderson JR Ullrich FA Obstetric anesthesia workforce survey: twenty-year update.Anesthesiology. 2005; 103: 645-653Crossref PubMed Scopus (243) Google Scholar In spite of the proposed benefits and increased use of intrapartum neuraxial analgesia, considerable debate has existed in the obstetric and anaesthesiology communities regarding the impact of neuraxial analgesia on the progress of labour and mode of delivery. While observational studies uniformly conclude that parturients who have neuraxial analgesia for labour have higher Caesarean and instrumental vaginal delivery rates and longer durations of labour, the cause–effect relationship of this association, particularly for the duration of labour and incidence of instrumental vaginal delivery, is unclear. The purpose of this article is to review and summarize the available evidence regarding the impact of neuraxial analgesia on labour outcomes and provide clinicians with a clearer understanding of the issues. Impact studies are a type of study design used to investigate the effect of a certain treatment modality on patient outcomes. Also known as before–after studies, these studies are designed to assess the incidence of a patient outcome before and after the implementation of a specific treatment. An advantage of this type of study design compared with the gold standard randomized controlled trial is that it eliminates the potential development of a Hawthorne effect. As such, in some circumstances, the external validity of the results from these studies might be more robust, as patients have not chosen to participate in the study, and therefore might present a more realistic representation of the general population. Additionally, this study design eliminates cross-over between treatment groups, as the control group is the time period before the treatment implementation. However, a limitation of this study design is the assumption that there were no other changes in the medical management of patients between the 'before' and 'after' time periods that could influence the outcome of interest. Yancey and colleagues11Yancey MK Pierce B Schweitzer D Daniels D Observations on labor epidural analgesia and operative delivery rates.Am J Obstet Gynecol. 1999; 180: 353-359Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar published the largest impact study investigating the impact of the introduction of neuraxial labour analgesia on Caesarean delivery rates by examining the incidence of Caesarean delivery at the Tripler United States Army Hospital in Hawaii before and after 1993. Before 1993, the rate of epidural analgesia in this hospital was less than 1%. In 1993, a policy change within the United States Department of Defense mandating on-demand availability of neuraxial labour analgesia in US military hospitals resulted in an increase in the rate of epidural labour analgesia to 80% over a 1-yr time period. Despite this increased use of neuraxial labour analgesia, the Caesarean delivery rate in nulliparous women in spontaneous labour remained unchanged (19.0% vs 19.4%). For years, the low Caesarean delivery rate at the National Maternity Hospital in Dublin, Ireland was partially attributed to the low rates of intrapartum epidural analgesia. However, Impey and colleagues12Impey L MacQuillan K Robson M Epidural analgesia need not increase operative delivery rates.Am J Obstet Gynecol. 2000; 182: 358-363Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar disproved this theory in an impact study comparing obstetric outcomes for the first 1000 nulliparous, term, spontaneously labouring parturients who delivered at the National Maternity Hospital in 1987 with similar groups of women who delivered in 1992 and 1994. The epidural analgesia rate increased during this time period (10% in 1987, 45% in 1992, and 57% in 1994), yet the Caesarean delivery rate remained unchanged (4% in 1987, 5% in 1992, and 4% in 1994; not significant). Based on these findings, the authors concluded that the initial low rates of epidural analgesia could not explain this institution's low rate of Caesarean delivery. Several other impact studies have shown no association between Caesarean delivery rates and rates of epidural administration.13Fogel ST Shyken JM Leighton BL Mormol JS Smeltzer J Epidural labor analgesia and the incidence of Cesarean delivery for dystocia.Anesth Analg. 1998; 87: 119-123Crossref PubMed Google Scholar, 14Gribble RK Meier PR Effect of epidural analgesia on the primary cesarean rate.Obstet Gynecol. 1991; 78: 231-234PubMed Google Scholar, 15Johnson S Rosenfield JA The effect of epidural anesthesia on the length of labor.J Fam Pract. 1995; 40: 244-247Crossref PubMed Google Scholar, 16Lyon DS Knuckles G Whitaker E Salgado S The effect of instituting an elective labor epidural program on the operative delivery rate.Obstet Gynecol. 1997; 90: 135-141Crossref PubMed Scopus (47) Google Scholar, 17Socol ML Garcia PM Peaceman AM Dooley SL Reducing cesarean births at a primarily private university hospital.Am J Obstet Gynecol. 1993; 168: 1748-1758Abstract Full Text PDF PubMed Scopus (83) Google Scholar These findings were confirmed in a meta-analysis by Segal and colleagues18Segal S Su M Gilbert P The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis.Am J Obstet Gynecol. 2000; 183: 974-978Abstract Full Text PDF PubMed Scopus (61) Google Scholar that included nine impact studies involving more than 37 000 parturients. There was no increase in the rate of Caesarean delivery during a period of increased usage of epidural analgesia compared with a historical control period (Fig. 1). Randomized controlled trials are the gold standard study design to investigate the impact of medical interventions on clinical outcomes, as they mitigate or eliminate the potential biases seen in other study designs, including impact studies. Unfortunately, randomized controlled trials of the effect of neuraxial labour analgesia on the progress of labour suffer a number of limitations. These trials cannot be placebo controlled, as it would be unethical to randomize women to a no-analgesia group, and presumably, few women would agree to participate in such a study. Another obvious limitation is the lack of blinding owing to the marked difference in the quality of analgesia between neuraxial and other types of analgesia. Additionally, because neuraxial analgesia is significantly superior to other forms of analgesia, many studies suffer from a high group cross-over rate. Other limitations include lack of control for other factors known to influence the Caesarean delivery rate, including parity, obstetric provider, labour management, and insurance status, among others. Given these limitations, multiple randomized controlled trials have investigated the effect of neuraxial analgesia on Caesarean delivery rates compared with systemic opioid analgesia. A 2005 Cochrane review involving 20 studies reported no increase in Caesarean delivery rates between women who received epidural vs systemic analgesia for labour (RR 1.07, 95% CI 0.93–1.23).1Anim-Somuah M Smyth R Howell C Epidural versus non-epidural or no analgesia in labour.Cochrane Database Syst Rev. 2005; 4: CD000331PubMed Google Scholar Similarly, a 2005 meta-analysis by Halpern and Leighton19Halpern SH Leighton BL Epidural analgesia and the progress of labor.in: Halpern SH Douglas MJ Evidence-based Obstetric Anesthesia. Blackwell, Oxford, UK2005: 10-22Crossref Scopus (4) Google Scholar of 17 studies involving 6701 women concluded that the risk of Caesarean delivery was no different between women who received systemic opioid vs neuraxial analgesia [odds ratio (OR) 1.03; 95% CI 0.86–1.22] (Fig. 2). Although differing in many variables (e.g. parity, type of neuraxial analgesia, cross-over rate, labour management), all of the studies analysed in these meta-analyses, save one, found no difference in Caesarean delivery rates between women who received neuraxial vs systemic analgesia. The single, dissenting study by Thorp and colleagues20Thorp JA Hu DH Albin RM et al.The effect of intrapartum epidural analgesia on nulliparous labor: a randomized, controlled, prospective trial.Am J Obstet Gynecol. 1993; 169: 851-858Abstract Full Text PDF PubMed Scopus (399) Google Scholar randomized 93 nulliparous women to receive epidural analgesia or systemic analgesia with meperidine. Twelve (25%) of the women in the epidural group underwent Caesarean delivery compared with one (2%) woman in the meperidine group. However, there were several flaws with this study's methodology and results which were of concern. First, the investigators were ultimately responsible for deciding the method of delivery, potentially leading to significant selection bias. Second, there was no standardization between groups of other factors known to influence labour outcomes, specifically timing and dose of oxytocin and timing of rupture of membranes. Third, there was an anomalous outcome in the Caesarean delivery rate for both groups: the Caesarean delivery rate in the epidural group was significantly higher, and that in the meperidine group significantly lower, than the historical norm (15%) for the study institution. Taken together, these study design flaws significantly limit the external validity and applicability of the results, and might have contributed to the anomalous results. Investigators from Parkland Hospital in Dallas, TX, USA also performed several randomized trials investigating this topic.4Ramin SM Gambling DR Lucas MJ Sharma SK Sidawi JE Leveno KJ Randomized trial of epidural versus intravenous analgesia during labor.Obstet Gynecol. 1995; 86: 783-789Crossref PubMed Scopus (285) Google Scholar 21Gambling DR Sharma SK Ramin SM et al.A randomized study of combined spinal-epidural analgesia versus intravenous meperidine during labor: impact on cesarean delivery rate.Anesthesiology. 1998; 89: 1336-1344Crossref PubMed Scopus (129) Google Scholar, 22Sharma SK Leveno KJ Update: epidural analgesia does not increase cesarean births.Curr Anesthesiol Rep. 2000; 2: 18-24Google Scholar, 23Sharma SK Sidawi JE Ramin SM Lucas MJ Leveno KJ Cunningham FG Cesarean delivery: a randomized trial of epidural versus patient-controlled meperidine analgesia during labor.Anesthesiology. 1997; 87: 487-494Crossref PubMed Scopus (201) Google Scholar This institution is unique in that its patient population is composed primarily of indigent Hispanic parturients. Labour was managed by the same group of resident physicians and midwives who were supervised by a core group of attending obstetricians. This distinctive organizational set-up eliminates several factors that are known to confound results of similar studies (i.e. parturient and obstetric provider variability, and labour management). In their first study, more than 1300 women of mixed parity were randomized to receive epidural bupivacaine-fentanyl or i.v. meperidine for labour analgesia.4Ramin SM Gambling DR Lucas MJ Sharma SK Sidawi JE Leveno KJ Randomized trial of epidural versus intravenous analgesia during labor.Obstet Gynecol. 1995; 86: 783-789Crossref PubMed Scopus (285) Google Scholar Although they demonstrated a Caesarean delivery rate of 9.0% in the epidural group vs 3.9% in the meperidine group, there was a lack of an intent-to-treat analysis of the data despite a high cross-over rate. As approximately one-third of the women in each group did not receive the treatment to which they were randomized, it was unclear whether there was actually a higher incidence of Caesarean delivery in the women randomly assigned to receive epidural analgesia. The investigators subsequently performed an intent-to-treat analysis that revealed a Caesarean delivery rate of 6% in both groups.22Sharma SK Leveno KJ Update: epidural analgesia does not increase cesarean births.Curr Anesthesiol Rep. 2000; 2: 18-24Google Scholar The authors, in hopes of decreasing the cross-over rate of the meperidine group, designed a second study in which meperidine was administered by patient-controlled i.v. analgesia (PCIA).24Sharma SK Alexander JM Messick G et al.Cesarean delivery: a randomized trial of epidural analgesia versus intravenous meperidine analgesia during labor in nulliparous women.Anesthesiology. 2002; 96: 546-551Crossref PubMed Scopus (142) Google Scholar Despite a significant number of women not receiving the treatment to which they were randomized owing to rapid labour, only 5 of 357 parturients in the PCIA group crossed-over to the epidural group. Again, the investigators found no difference in the rate of Caesarean delivery between groups; using an intent-to-treat analysis, the Caesarean delivery rate was 4% in the epidural group vs 5% in the PCIA group. In a third randomized trial, the Parkland investigators randomized women of mixed parity to receive combined spinal–epidural (CSE) analgesia (intrathecal sufentanil 10 µg, followed by epidural bupivacaine with fentanyl at the second request for analgesia) or i.v. meperidine (50 mg h−1 on request).21Gambling DR Sharma SK Ramin SM et al.A randomized study of combined spinal-epidural analgesia versus intravenous meperidine during labor: impact on cesarean delivery rate.Anesthesiology. 1998; 89: 1336-1344Crossref PubMed Scopus (129) Google Scholar Although only 60% of the parturients received the treatment to which they were allocated, an intent-to-treat analysis of the data revealed a Caesarean delivery rate of 6% in the CSE group vs 5.5% in the meperidine group. Finally, the Parkland investigators conducted an individual patient meta-analysis of all previous studies (n=4465) comparing Caesarean delivery rates in women randomized to epidural analgesia vs systemic opioids; the OR for Caesarean delivery was 1.04 (95% CI 0.81–1.34).25Sharma SK McIntire DD Wiley J Leveno KJ Labor analgesia and cesarean delivery: an individual patient meta-analysis of nulliparous women.Anesthesiology. 2004; 100: 142-148Crossref PubMed Scopus (119) Google Scholar The results of these studies suggest that the administration of neuraxial analgesia, by itself, does not increase the risk of Caesarean delivery. Dose–response studies have been performed to determine if the concentration of local anaesthetic impacts Caesarean delivery rates. The COMET study investigated this association by randomizing more than 1000 women to one of three labour analgesia regimens: (i) 'high-dose' epidural (intermittent boluses of bupivacaine 0.25%); (ii) 'low-dose' epidural (continuous infusion of bupivacaine 0.1% and fentanyl 2 µg ml−1); or (iii) 'low-dose' CSE (intrathecal bupivacaine 2.5 mg/fentanyl 25 µg, followed by intermittent boluses of bupivacaine 0.1% and fentanyl 2 µg ml−1).26Comparative Obstetric Mobile Epidural Trial Study Group UK Effect of low-dose mobile versus traditional epidural techniques on mode of delivery: a randomised controlled trial.Lancet. 2001; 358: 19-23Abstract Full Text Full Text PDF PubMed Scopus (255) Google Scholar The investigators found no difference in the Caesarean delivery rate among the three groups. Similarly, three other randomized controlled trials found no difference between groups in terms of Caesarean delivery rates despite differences in local anaesthetic concentrations.27Collis RE Davies DW Aveling W Randomised comparison of combined spinal-epidural and standard epidural analgesia in labour.Lancet. 1995; 345: 1413-1416Abstract PubMed Scopus (245) Google Scholar, 28Nageotte MP Larson D Rumney PJ Sidhu M Hollenbach K Epidural analgesia compared with combined spinal-epidural analgesia during labor in nulliparous women.N Eng J Med. 1997; 337: 1715-1719Crossref PubMed Scopus (196) Google Scholar, 29Olofsson C Ekblom A Ekman-Ordeberg G Irestedt L Obstetric outcome following epidural analgesia with bupivacaine-adrenaline 0.25% or bupivacaine 0.125% with sufentanil: a prospective randomized controlled study in 1000 parturients.Acta Anaesthesiol Scand. 1998; 42: 284-292Crossref PubMed Scopus (51) Google Scholar These results suggest that 'high-dose' neuraxial analgesia does not result in a higher risk for Caesarean delivery compared with 'low-dose' analgesia. Additionally, as several of these studies compared CSE vs epidural analgesia, these results imply that the mode of neuraxial analgesia does not affect the risk of Caesarean delivery. Data from observational studies suggest an association between Caesarean delivery and the initiation of neuraxial analgesia during early labour (usually defined as cervical dilation less than 4–5 cm).30Lieberman E Lang JM Cohen A D'Agostino Jr, R Datta S Frigoletto Jr, FD Association of epidural analgesia with cesarean delivery in nulliparas.Obstet Gynecol. 1996; 88: 993-1000Crossref PubMed Scopus (150) Google Scholar 31Thorp JA Eckert LO Ang MS Johnston DA Peaceman AM Parisi VM Epidural analgesia and cesarean section for dystocia: risk factors in nulliparas.Am J Perinatol. 1991; 8: 402-410Crossref PubMed Scopus (113) Google Scholar Based on these observations, the American College of Obstetricians and Gynecologists (ACOG) recommended for many years that women delay requesting epidural analgesia, 'when feasible, until the cervix is dilated to 4–5 cm.'32American College of Obstetricians and Gynecologists Obstetric analgesia and anesthesia. ACOG Practice Bulletin No. 36, July 2002.Obstet Gynecol. 2002; 100: 177-191Crossref PubMed Scopus (94) Google Scholar However, similar to the cause-and-effect question raised regarding the association of neuraxial analgesia with the risk of Caesarean delivery, the question arises as to whether early initiation of neuraxial labour analgesia is directly responsible for adverse labour outcomes, or is merely associated with an increased risk of Caesarean delivery. Randomized controlled trials have addressed this issue by comparing early-labour neuraxial analgesia to systemic opioid analgesia followed by neuraxial analgesia at a cervical dilation of 4–5 cm.33Chestnut 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: 1201-1208Crossref PubMed Scopus (164) Google Scholar, 34Chestnut DH Vincent RD McGrath JM Choi WW Bates JN Does early administration of epidural analgesia affect obstetric outcome in nulliparous women who are receiving intravenous oxytocin?.Anesthesiology. 1994; 80: 1193-1200Crossref PubMed Scopus (144) Google Scholar, 35Luxman D Wolman I Groutz A et al.The effect of early epidural block administration on the progression and outcome of labor.Int J Obstet Anesth. 1998; 7: 161-164Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 36Ohel G Gonen R Vaida S Barak S Gaitini L Early versus late initiation of epidural analgesia in labor: does it increase the risk of cesarean section? A randomized trial.Am J Obstet Gynecol. 2006; 194: 600-605Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar, 37Wong CA Scavone BM Peaceman AM et al.The risk of cesarean delivery with neuraxial analgesia given early versus late in labor.N Engl J Med. 2005; 352: 655-665Crossref PubMed Scopus (286) Google Scholar Two studies by Chestnut and colleagues33Chestnut 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: 1201-1208Crossref PubMed Scopus (164) Google Scholar,34Chestnut DH Vincent RD McGrath JM Choi WW Bates JN Does early administration of epidural analgesia affect obstetric outcome in nulliparous women who are receiving intravenous oxytocin?.Anesthesiology. 1994; 80: 1193-1200Crossref PubMed Scopus (144) Google Scholar randomized nulliparous women in spontaneous labour or those receiving oxytocin augmentation to one of the two groups: early epidural analgesia or early i.v. nalbuphine analgesia followed by epidural analgesia when cervical dilation reached 5 cm. Although the investigators found no difference in Caesarean delivery rates between groups, the median cervical dilation at the time of initiation of analgesia was 3.5 cm in spontaneous women and 4.0 cm in women receiving oxytocin augmentation. Therefore, the external validity of the results is limited, as women, especially those undergoing an induction of labour or those with premature rupture of membranes, often request analgesia at cervical dilations less than 3 cm. Consequently, two randomized trials—one by Wong and colleagues37Wong CA Scavone BM Peaceman AM et al.The risk of cesarean delivery with neuraxial analgesia given early versus late in labor.N Engl J Med. 2005; 352: 655-665Crossref PubMed Scopus (286) Google Scholar and the other by Ohel and colleagues36Ohel G Gonen R Vaida S Barak S Gaitini L Early versus late initiation of epidural analgesia in labor: does it increase the risk of cesarean section? A randomized trial.Am J Obstet Gynecol. 2006; 194: 600-605Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar—compared the initiation of early-labour neuraxial analgesia with systemic opioid analgesia in women whose median cervical dilation at initiation of analgesia was 2 cm. Similar to the results of the studies by Chestnut, neither was there a difference in the rate of Caesarean delivery in the two groups, nor was there a difference in the rate of instrumental vaginal delivery. As a result of these latter studies, in 2006 the ACOG published an updated Committee Opinion entitled Analgesia and Caesarean Delivery Rates, stating that: 'In the absence of a medical contraindication, maternal request is a sufficient medical indication for pain relief during labour. The fear of unnecessary cesarean delivery should not influence the method of pain relief that women can choose during labour.' 38American College of Obstetricians and Gynecologists Committee on Obsteteric Practice Analgesia and cesarean delivery rates. ACOG Committee Opinion No. 339, June 2006.Obstet Gynecol. 2006; 107: 1487Crossref PubMed Google Scholar Similarly, a 2007 joint statement by the Royal College of Obstetricians and Gynaecologists, the Royal College of Midwives, the Royal College of Anaesthetists, and the Royal College of Paediatrics and Child Health stated: 'When women chose epidural analgesia for pain relief in labour, they should be able to receive it in a reasonable time. This means that obstetric units should be able to provide regional analgesia on request at all times.'39Royal College of Obstetricians and Gynaecologists, Royal College of Midwives, Royal College of Anaesthetists, Royal College of Paediatrics and Child Health Safer Childbirth: Minimum Standards for the Organisation and Delivery of Care in Labour. RCOG Press at the Royal College of Obstetricians and Gynaecologists, London2007Google Scholar The results of these studies have been further confirmed by two more recent randomized controlled trials. A 2009 trial by Wang and colleagues40Wang F Shen X Guo X Peng Y Gu X Epidural analgesia in the latent phase of labor and the risk of cesarean delivery: a five-year randomized controlled trial.Anesthesiology. 2009; 111: 871-880Crossref PubMed Scopus (99) Google Scholar over a 5-yr period involving more than 12 000 nulliparas demonstrated no increase in Caesarean delivery rates in parturients randomized to receive epidural analgesia in the latent phase when compared with active phase of labour (23.2% vs 22.8%, P=0.51). Similarly, in women undergoing induction of labour, Wong and colleagues41Wong CA McCarthy RJ Sullivan JT Scavone BM Gerber SE Yaghmour EA Early compared with late neuraxial analgesia in nulliparous labor induction: a randomized controlled trial.Obstet Gynecol. 2009; 113: 1066-1074Crossref PubMed Scopus (59) Google Scholar found no difference in Caesarean delivery rates between parturients randomized to receive neuraxial analgesia early in labour (cervical dilation <4 cm) vs later in labour (32.7% vs 31.5%, P=0.65). Finally, a meta-analysis of eight randomized controlled trials and cohort studies of early-labour vs late-labour initiation of neuraxial analgesia (n=3320) demonstrated that early initiation of neuraxial analgesia does not increase the rate of Caesarean delivery.42Marucci M Cinnella G Perchiazzi G Brienza N Fiore T Patient-requested neuraxial analgesia for labor: impact on rates of cesarean and instrumental vaginal delivery.Anesthesiology. 2007; 106: 1035-1045Crossref PubMed Scopus (56) Google Scholar Observational data suggest an association between neuraxial labour analgesia and instrumental vaginal delivery, i.e. forceps delivery or vacuum extraction. Similar to the data of studies investigating the effect o
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