Worldwide, rising caesarean section rates are a major public health concern (Boerma et al, 2018). In the absence of a clear medical indication (including mental health), a caesarean section offers no benefit to mother and baby (World Health Organization, 2023). However, caesarean sections are associated with increased risk of infection, blood clots and bleeding in women, abnormal placentation and stillbirth in future pregnancies and transitory tachypnea of the newborn (Sandall et al, 2018).
The link between epidural analgesia in labour and increased risk of an emergency caesarean section has been debated for decades (Chestnut, 1997; Segal et al, 2000; Klein, 2006; Kotaska et al, 2006; Newnham et al, 2016). The often-quoted rationale for the increased risk of emergency caesarean section for women with epidural analgesia is that some women choosing epidural have an ‘intrinsically difficult and ultimately obstructed labor’ (Alexander et al, 2001). There is an argument that women with long latent stage and delays in the first stage of labour often experience fetal malposition and/or cephalopelvic disproportion causing excessively painful labours; therefore the cause of the increased risk of emergency caesarean section in these women is malposition and/or cephalopelvic disproportion rather than epidural analgesia (Wuitchik et al, 1989; Leighton and Halpern, 2002; Arulkumaran, 2012). However, this line of thinking is disputed (Lieberman et al, 2005).
The author works as a midwife in an obstetric-led unit in a busy London teaching hospital with approximately 6500 births every year. Based on information the author has from the unit, approximately 85–90% of women labouring in the obstetric-led unit are high risk. The rest are low risk, and their presence is determined by the decision to have epidural analgesia as their primary mode of pain relief. Adjacent to the obstetric-led unit is a midwifery-led unit used by low-risk women who do not require epidural analgesia. This unit cares for approximately 15% of the total women giving birth in the trust.
For the purposes of this article, high risk is defined as per the trust's guideline, including induction of labour for any reason, trial of labour after a previous caesarean section, augmentation with oxytocin infusion for delays in the first or second stage of labour, premature labour etc. Low-risk is defined as women suitable for midwifery-led intrapartum care.
The obstetricic-led unit has an anaesthetic service that provides prompt and efficient epidural analgesia. It has three anaesthetists on duty during the day (when elective caesarean sections take place) and two on duty at night. In the vast majority of cases, epidural analgesia is set up within 1 hour of the request being made, if the woman is already on the obstetric-led unit. If the woman is on the adjacent midwifery-led unit, the transfer time is usually within 1 hour, making the total wait for epidural analgesia less than 2 hours. In 2022, the author carried out an unpublished service evaluation and found that epidural uptake was 41.8%.
The induction rate at the trust is relatively high by UK standards (Taylor et al, 2024), with approximately 40% of all women at the trust contemplating a vaginal birth being induced. Women on the induction of labour pathway are routinely offered epidural analgesia prior to starting the oxytocin infusion; the vast majority accept.
A Cochrane review by Anim-Somuah et al (2018) concluded that epidural analgesia in labour does not increase the risk of emergency caesarean section. An earlier Cochrane review stated that early versus delayed epidural had no effect on the risk of emergency caesarean section (Sng et al, 2014). However, these conclusions ran contrary to the author's clinical experience and that of her midwifery colleagues. While randomised controlled trials are placed higher in the hierarchy of evidence (Bowling, 2014), midwifery experience is also considered evidence (Siddiqui, 2005). The National Institute for Health and Care Excellence (2022) guidelines state that ‘evidence can be obtained from a wide range of sources, including randomised controlled trials, observational studies and expert opinions of practitioners, people using services, family members and carers’.
To explore the discrepancy between the review findings and the author's expeiences, a personal evaluation of mode of birth for labours with and without epidural analgesia was carried out. The evaluation was restricted to women that the author had personally provided with any intrapartum care. This restriction was because of the work involved in establishing mode of birth if a woman gave birth after the author's shift finished, before the trust intrapartum records were computerised. The aim of the review was to compare mode of birth for 200 consecutive labours for women with and without epidural analgesia.
Methods
This was a retrospective review of birth outcomes for 200 consecutive labours of women for whom the author provided any intrapartum care between 21 July 2020 and 24 June 2022. Intrapartum care was defined as care given when either the woman was ≥4cm dilated or receiving oxytocin infusion as part of labour induction or the labour augmentation pathway, in line with trust guidelines for one-to-one care.
Service evaluations commonly use a specified timeframe or specified sample, rather than performing a sample size calculation (Bowling, 2014). A sample of 200 women was selected for this study as it was thought to be sufficient to show a trend. Convenience sampling was used to select all women for whom the author provided any intrapartum care until the sample of 200 was reached; this took 23 months. Those excluded were women in latent stage and established labour or on oxytocin infusion where the author's care was provided as break-relief for the case midwife. One case of a spinal sited at full dilatation was also excluded.
After the author presented this personal service evaluation at a multidisciplinary team meeting involving obstetricians, anaesthetists and midwives, she subsequently undertook an epidural service evaluation for the entire trust for the whole of 2022. This evaluation included all women with a singleton baby in cephalic presentation at ≥37 weeks' gestation, delivered at St Thomas' by category 1 or 2 caesarean section, foreps, ventouse or spontaneous vaginal birth. It excluded those who gave birth by category 3 or 4 caesarean section and those in breech presentatiuon. The data were compiled by the trust's IT department.
Data collection and analysis
The author collected routinely available data including age, body mass index at booking, body mass index at birth (if recorded on the postnatal ward), parity, gestation, risk factors at the time active labour was established or oxytocin infusion was commenced for women without epidural analgesia, risk factors for when epidural was sited for women with epidural analgesia, risk factors at birth, mode of birth (spontaneous vaginal birth, ventouse, forceps, emergency caesarean section) and baby's weight.
For women with epidural analgesia, risk status (high/low) was determined when epidural was sited. For women who never requested or received epidural analgesia, risk status was determined at the time active labour was established (when the woman was ≥4cm dilated) or oxytocin infusion was commenced.
The data were analysed in Microsoft Word, through generation of descriptive statistics and pie charts.
Ethical considerations
The personal and trust-wide service evaluations were approved by the head of audit for maternity. As the service evaluations only analysed routinely collected data, no ethics committee approval and/or consent was deemed necessary. Data were anonymised at the point of collection to ensure confidentiality.
Results
The mode of birth results for women with and without epidural analgesia in the author's personal evaluation are shown in Figure 1. Epidural analgesia in labour was associated with more than a two-fold increase in the risk of an emergency caesarean section. The findings from the trust-wide evaluation are shown in Figure 2, which were comparable to the personal service evaluation.
For the personal study, the risk of emergency caesarean section in relation to risk status was explored. There was an increase in risk for women who received epidural analgesia, regardless of their underlying obstetric risk (Figures 3 and 4). Unfortunately, because of time constraints, it was not possible to collate the data separately for low- and high-risk women for the entire trust.
Discussion
The results of the personal evaluation showed an increase in the risk of emergency caesarean section in women who received epidural analgesia, regardless of their underlying obstetric risk. This is in line with other cohort studies, which are considered the second best level of evidence after a randomised controlled trial (Murad et al, 2016).
The second largest cohort study worldwide was conducted by Bannister-Tyrrell et al (2014). The team analysed the labour records of 210 718 mostly low-risk women, including those with prolonged rupture of membranes and pregnancy beyond 41 weeks, on the basis of evidence that induction of labour for those reasons does not increase the risk of emergency caesarean section. The authors used propensity scores matching and logistic regression techniques to match 52 604 of the 66 317 women who received epidural analgesia in labour to a control group without analgesia. They reported that epidural analgesia was associated with a 2.5 fold increase in the risk of emergency caesarean section. After accounting for confounders, the authors concluded that epidural analgesia was associated with a 50% increase in the risk of emergency caesarean section. They argued that while randomised controlled trials provide important information, their findings would not necessarily be generalisable to every clinical setting and every population; therefore the findings from population-based studies should be taken into account by women and clinicians when discussing pain relief in labour.
The largest UK cohort study of 64 538 low-risk women concluded that by choosing to start labour in the midwifery-led unit or at home, a low-risk primip was reducing the risk of emergency caesarean section by half compared to starting labour in the obstetric-led unit (Brocklehurst et al, 2011). The risk reduction was more pronounced for low-risk women having their second, third and fourth babies. The advantage of this study was that it explored labour outcomes on intent-to-treat analysis, where women's outcomes were analysed in relation to their birthplace decisions made while they were still pregnant. The authors did not comment on the possible reasons for the vast discrepancy in findings, which may have been the result of the availability of epidural analgesia, the women's underlying characteristics (for example, the presence or absence of anxiety), the position of women in labour, midwifery skill or the obstetric overmanagement of low-risk women.
There is a large body of research that shows that women whose labours are classified as high risk are more likely to undergo an emergency caesarean section or instrumental birth (Ye et al, 2022; Bromfield et al, 2023; Carroll et al, 2023). Observational studies, such as the present personal review, can only establish association, while randomised controlled studies are considered the golden standard to establish cause and effect (Bowling 2014). Nevertheless, the author felt that the discrepancy in the findings from the author's observational study and the Cochrane review warranted exploration.
A closer look at the Cochrane review studies revealed that the majority were of low-risk women in spontaneous labour who were 3–5cm dilated by the time they received epidural analgesia, other forms of pain relief or no pain relief at all in some studies (Anim-Somuah et al, 2018). Additionally, active or modified active labour management was used in the majority of studies. Active labour management was developed in Ireland in the 1960s and includes amniotomy as soon as the woman is ascertained to be in established labour, 1–2 hourly vaginal examinations, early and aggressive use of oxytocin augmentation and continuous support by a qualified midwife or nurse (O'Driscoll et al, 1984; Bohra et al, 2003). Kotaska et al (2006) analysed the findings of eight early randomised controlled trials, aiming to elucidate the relationship between epidural analgesia and risk of emergency caesarean section in low-risk women. Active labour management and associated aggressive use of oxytocin was used in seven of the eight studies; those studies showed that epidural had no effect of the risk on an emergency caesarean section. The only study with low-dose oxytocin showed a marked increase in the risk of emergency caesarean section.
There is an argument that active labour management decreases the risk of emergency caesarean section (O'Driscoll et al, 1984; Bohra et al, 2003). This assertion is disputed by a Cochrane review that found no effect (Brown et al, 2013). A further Cochrane review concluded that active labour management is associated with a higher risk of uterine hyperstimulation (Budden et al, 2014). As active labour management is not practiced in the author's trust, the findings of the majority of studies in the Cochrane review (Anim-Somuah et al, 2018) cannot be generalised to the women in her care.
Once the author excluded all studies involving low-risk women in spontaneous labour, pre-eclamptic women only and clearly stated active labour management, only one study remained (Freeman et al, 2015). This study is the largest in the Cochrane review, with 1358 ‘intermediate to high risk’ nulliparous and parous women giving birth across 15 obstetric-led units in the Netherlands. This group of women seems to most closely reflect the 171 high-risk women cared for by the author of the present study. Freeman et al (2015) compared labour outcomes for women with epidural analgesia versus intravenous remifentanil, and their findings are shown in Figure 5. Emergency caesarean section rates were 15.0% in both groups, compared to 36.8% in high-risk epidural and 14.0% in high-risk non-epidural groups in the personal service evaluation (Figure 4).
There are several possible reasons for the difference in findings between the present study and Freeman et al (2015). The discrepancy may be the result of a combination of reasons explored below. One explanation is the use of different anaesthetic practices. In the author's trust, women are encouraged to maintain epidural block to the level necessary to eliminate any pain. The Netherlands team used a different approach, as ‘Dutch guidelines advise the continuation of epidural analgesia during second stage provided there is no effect on motor function…in the Netherlands it is still practice to wait for the urge to push (and even to stop the epidural to increase sensation’ (Freeman et al, 2015). A light epidural was also a common feature of many of the Cochrane review studies (Anim-Somuah et al, 2018). The following quote from one of the studies included in the review provides a summary of the analgetic approach used in many of the studies: ‘our anesthesiologists provided the best level of pain relief possible without significant impairment to the patient's expulsive efforts. Clearly, a regional technique with significant motor involvement below the T-10 level will predispose to inadequate expulsive efforts. The pain scores…demonstrate that we greatly ameliorated, but did not entirely abolish, the pain of labor with this analgesic technique’ (Bofill et al, 1997).
There is good quality research that heavy epidural block predisposes rotation to the occipito-posterior position, thought to be the result of relaxation of the pelvic floor muscles (Hoult et al, 1977; Saunders et al, 1989). The degree of malrotation is thought to be in proportion to the degree of the epidural motor block (Gaiser, 2005) and new regimens of epidural medication (mobile epidurals) ameliorate the disadvantages of earlier epidurals (Comparative Obstetric Mobile Epidural Trial (COMET) Study Group UK, 2001). However, Lieberman et al (2005) found a 4-fold increase in the incidence of occipito-posterior position even with the new anaesthetic technique; their study did not report on the degree of motor block. Additionally, high-quality evidence from ultrasound studies shows that babies change position frequently in labour; only a minority of babies start labour in occipito-anterior position and two-thirds in occipito-posterior positions at birth start at occipito-anterior in early labour or before induction of labour (Gardberg et al, 1998; Peregrine et al, 2007; Ahmad et al, 2014). Malrotation or failure to rotate to occipito-anterior position vastly increases the woman's risk of emergency caesarean section, instrumental birth and third and fourth degrees tears (Fitzpatrick et al, 2001; Cheng et al, 2006; Choi et al, 2016).
Another reason for the discrepancy in findings might be related to the fact that women in Freeman et al's (2015) study were considerably more dilated by the time they received epidural analgesia compared to the women in the author's trust. Median dilatation was 4cm (3–5cm) for both remifentanil and epidural groups in Freeman et al (2015). In the author's trust practice, until recently, women were routinely advised to have epidural sited before commencing oxytocin infusion, commonly at 1–2 cm dilation.
Another Cochrane review of seven studies concluded that early epidural does not increase the risk of emergency caesarean section compared to late epidural (Sng et al, 2014). However, five of the included studies were of low-risk nulliparous women at term in spontaneous labour. These findings cannot be generalised to the majority of women in the obstetric-led unit at the author's trust. Two randomised controlled trials in Sng et al's (2014) review analysed outcomes for women in induced labour and found no difference in the risk of emergency caesarean section (Chestnut et al, 1994: Wong et al, 2009). However, in neither study was epidural analgesia commenced prior to oxytocin infusion which, until recently, was a standard practice in the author's trust.
There is an argument that delaying epidural to allow for the flexion of the baby's head benefits labour progress and reduces the risk of emergency caesarean section (Klein, 2006). Additionally, the longer the duration of epidural analgesia, the heavier the epidural block (COMET Study Group, 2001), making it more likely the baby will malrotate to the occipito-posterior position (Hoult et al, 1977; Saunders et al, 1989), which is strongly associated with increased risk of emergency caesarean section (Fitzpatrick et al, 2001; Cheng et al, 2006; Choi et al, 2016). Furthermore, epidural analgesia is significantly more likely to cause fever in labour, with the incidence of fever correlated to the duration of exposure to epidural analgesia. Fever is associated with a 4-fold increase in the risk of hypoxic injury to the baby's brain. As a result, more women with fever in labour undergo an emergency caesarean section (Goetzl, 2023).
Freeman et al (2015) did not comment on the positions women adopted in labour. Labouring women hardly ever adopt a semi-recumbent position unless directed by a healthcare professional; this might be related to the fact that a semi-recumbent position is often the most painful in unmedicated labour (Priddis et al, 2012). It is possible that the default semi-recumbent position for women with epidural analgesia in the author's trust combined with heavy epidural block may have contributed to the increased risk of emergency caesarean section in this retrospective study. A recent systematic review and meta-analysis concluded that placing women with epidural analgesia into a lateral position with a peanut ball led to an 11% increase in the chance of vaginal birth (Delgado et al, 2022). This makes sense in view of the research that epidural analgesia predisposes malrotation to the occipito-posterior position.
A further explanation for the discrepancy in findings between Freeman et al's (2015) study and the personal retrospective service evaluation might be related to the evidence that women taking part in an obstetric or gynaecology randomised controlled trial experience better outcomes compared to women receiving routine care. A systematic review and meta-analysis of 21 women's health studies (20 160 women, 4759 outcome events) concluded that trial participants had 25% better odds of improved outcomes on average, compared with non-participants (Nijjar et al, 2017).
Informed choice is a cornerstone of modern medicine (Department of Health, 2009; British Medical Association, 2024). Anim-Somuah et al (2018) concluded that women choosing epidural analgesia in labour were more likely to experience intrapartum pyrexia requiring broad spectrum antibiotics, receive oxytocin augmentation, undergo instrumental birth and experience urinary retention in postpartum period. Women should be made aware of this evidence that epidural analgesia can affect the course of their labour and postpartum experience, especially as there is no evidence that pain relief on its own enhances the woman's experience. Three of the studies in Anim-Somuah et al's (2018) review specifically assessed women's satisfaction with childbirth experience, rather than pain scores alone. Howell et al (2001) reported that ‘no significant differences between the two groups were seen (epidural versus intramuscular pethidine). Early and late maternal satisfaction with the experience of childbirth and with pain relief was high in both groups’. Dickinson et al (2003) noted that ‘maternal satisfaction with intrapartum analgesia was significantly higher with epidural analgesia than non-epidural analgesic techniques. Overall satisfaction scores for labour and delivery were high regardless of analgesic approach, reflecting the multiple issues other than pain relief that are involved in the childbirth experience’. Finally, Orange et al (2012) reported that ‘maternal satisfaction with the technique of pain relief and with delivery was higher in the [combined spinal-epidural] group, and around 97% of the patients would repeat the same technique at future deliveries compared to 82.4% of the women in the group using only non-pharmacological methods’.
Implications for practice
A systematic review of 137 studies (Hodnett, 2002) revealed that ‘four factors—personal expectations, the amount of support from caregivers, the quality of the caregiver-patient relationship, and involvement in decision making—appear to be so important that they override the influences of age, socioeconomic status, ethnicity, childbirth preparation, the physical birth environment, pain, immobility, medical interventions, and continuity of care, when women evaluate their childbirth experiences’. It is clear that epidural analgesia is popular with women (Borrelli et al, 2020), yet the findings from Anim-Somuah et al's (2018) and Sng et al's (2014) randomised controlled trials do not seem to hold in the context of a busy obstetric-led labour ward in a central London hospital.
Following the author's presentation at the multidisciplinary meeting, there has been a marked shift from instructing women to ‘press epidural button every hour’ to pressing it only when the woman starts experiencing an unpleasant sensation. There has also been a marked uptick in the use of peanut balls. Additionally, many more women are starting oxytocin infusion without epidural analgesia in situ. The author is considering another service evaluation to establish whether these changes in practice will lead to a meaningful reduction in the risk of operative birth.
Limitations
The study has a number of limitations, including the small sample of 200 labours and that the author provided at least some intrapartum care for every woman in the study. The author was physically present at less than half of the births because of shift work. Her intrapartum care was on occasion limited to less than 1 hour.
Conclusions
This retrospective service evaluation of mode of birth in 200 consecutive labours with and without epidural analgesia revealed a more than two-fold increase in the risk of emergency caesarean section in the epidural group, regardless of the underlying obstetric risk. Further research on the potential link between risk of emergency caesarean section and epidural analgesia in labour is warranted.