A randomised clinical trial comparing the effects of delayed versus immediate pushing with epidural analgesia on mode of delivery and faecal continence

Authors


*Correspondence: Professor C. O'Herlihy, Department of Obstetrics and Gynaecology, National Maternity Hospital, University College Dublin, Holles Street, Dublin 2, Ireland.

Abstract

Objective To assess the effects of delayed vs immediate pushing in second stage of labour with epidural analgesia on delivery outcome, postpartum faecal continence and postpartum anal sphincter and pudendal nerve function.

Design Prospective, randomised, controlled trial.

Setting Tertiary referral maternity teaching hospital.

Population One hundred and seventy nulliparous women randomised at full dilatation to immediate or delayed pushing.

Methods A total of 178 nulliparous women, all with continuous epidural analgesia, were randomised at full cervical dilatation, but before the fetal head had reached the pelvic floor, to either immediate pushing or 1 hour delayed pushing. Labour outcome was analysed and all women underwent postpartum assessment of anal sphincter function, including anal manometry. Those women who had a normal delivery underwent neurophysiology studies, while those women who had an instrumental delivery underwent endoanal ultrasound.

Main outcome measures Mode of delivery; altered faecal continence.

Results Ninety women were randomised to immediate pushing and 88 to delayed pushing. The spontaneous delivery rate was 56% (50/90) in the immediate pushing group and 52% (46/88) in the delayed pushing group. Mean duration of labour for the immediate pushing group was 427 minutes compared with 480 minutes for the delayed pushing group (P= 0.005). Eighty-four percent (76/90) of women in the immediate pushing group received oxytocin to augment labour, 21/76 (28%) in the second stage only. Eighty-one percent (71/88) of women in the delayed pushing group received oxytocin to augment labour, 22/71 (31%) in the second stage only. Fetal outcome did not differ between the two groups. Episiotomy rates were 73% and 69% in the immediate pushing and delayed pushing groups, respectively. 26% (23/90) of the immediate pushing group and 38% (33/88) of the delayed pushing group complained of altered faecal continence after delivery (NS). Manometry, ultrasound and neurophysiology studies did not differ significantly between the two groups. Overall, 55% of women after instrumental delivery had endosonographic evidence of damage to the external anal sphincter, while 36% of women after spontaneous delivery had abnormal neurophysiology studies.

Conclusions Rates of instrumental delivery were similar following immediate and delayed pushing, in association with epidural analgesia. Delayed pushing prolonged labour by 1 hour but did not result in significantly higher rates of altered continence or anal sphincter injury, when compared with immediate pushing.

Introduction

In recent years, widespread use of epidural analgesia in labour has prompted extensive investigation of its effects on the progress of labour, mode of delivery and neonatal outcome. Epidural analgesia may abolish release of oxytocin in the second stage of labour due to its effects on pelvic autonomic nerves and, as a consequence, may lead to an increase in instrumental delivery1. Use of oxytocin has been proposed as one method of reducing this effect2, as has the practise of prolonging the second stage of labour by delaying active pushing3,4. The latter practise has become widespread in maternity units, despite conflicting evidence concerning its efficacy. A recent multicentre trial suggested that delayed pushing was an effective strategy in reducing the number of difficult deliveries among nulliparous women5 but other investigators have failed to show an improvement6,7. In addition, epidural analgesia, by relaxing the pelvic floor, may allow greater control over delivery of the fetal head and thereby reduce the risk of perineal laceration8.

Nevertheless, investigations of the effects of both epidural analgesia and delayed pushing on pelvic floor physiology and postpartum faecal continence have proved contradictory. It has been suggested that the associated increase in instrumental delivery rate increases the risk of mechanical trauma to the anal sphincter9. Furthermore, sustained pressure on the pudendal nerve as a result of prolongation of the second stage of labour has been implicated in the development of pudendal neuropathy10.

The incidence of epidural analgesia has increased markedly in our institution from 9% in 1989 to 50% in 1999, so that two-thirds of primiparae now receive this form of pain relief during labour. Delayed pushing in the second stage of labour in the presence of epidural blockade has become common practise in first labours, which are otherwise managed uniformly according to a protocol of Active Management11. The aim of this study was to compare the outcome of primiparous vaginal delivery in women with epidural analgesia randomised to either delayed pushing or immediate pushing following full cervical dilatation and to assess whether immediate pushing altered the rates of instrumental delivery. The study end-points were mode of delivery, alteration in postpartum faecal continence and injury to the anal sphincter mechanism.

Methods

Primiparae were recruited antenatally at 28–32 weeks of gestation during a one-year period (July 1998–July 1999). Written informed consent was obtained and prior ethical approval had been granted by the Hospital Research Ethics Committee. Patients with diabetes, irritable bowel syndrome or other bowel or neurological disorder were excluded from the study. Women were eligible for inclusion in the trial if they were in either spontaneous or induced labour with a singleton fetus, cephalic presentation between 37 and 42 weeks of gestation and had effective epidural analgesia in situ. All epidurals were administered via continuous infusion of 0.1% bupivicaine plus 2 μm/mL fentanyl citrate (Sublimaze; Janssen Pharmaceutica, Piscataway, New Jersey, USA) at a rate of 8–10 mL/hour.

Upon diagnosis of full dilatation, a numbered sealed opaque envelope containing computer-generated random allocations in a ratio of 1:1 in balanced blocks of 10, was opened and the patient was randomised by the attending midwife to either immediate pushing or to a 60-minute delay, prior to the commencement of active pushing. Patients were excluded if the vertex was visible at the introitus. Labours were managed according to the Active Management protocol11, which included early amniotomy and subsequent augmentation with intravenous oxytocin if cervical dilatation did not progress at 1 cm per hour. Continued or de novo use of oxytocin in the second stage of labour was at the discretion of the supervising midwife. Active pushing is limited to approximately 60 minutes in primiparae in our institution and this practise was retained for trial participants. If delivery was not imminent after 60 minutes pushing, a decision was made regarding the need for instrumental or caesarean delivery. All forceps and vacuum deliveries within our unit are low cavity and performed only if the fetal head is visible at the introitus. The use of rotational forceps is excluded.

Three months following delivery, patients were reviewed at a specialised perineal clinic during which a routine postnatal examination was performed and obstetric data were gathered from the hospital chart. A detailed bowel function questionnaire was completed by the participants and faecal continence was documented using a modified continence score12, with a score of 0 implying complete continence and a score of 20 implying complete incontinence. Faecal urgency was noted specifically and deemed significant if the patient was unable to defer defaecation for greater than 5 minutes, consistent with a debilitating impact on lifestyle and return to normal activity postpartum. Perineal pain, assessment of patient satisfaction with management of labour and preferred mode of delivery on subsequent pregnancies were also documented.

All patients underwent anal manometry. This was performed using a commercially available lower gastrointestinal system (PC Polygraf HR, Synectics Medical, Enfield, UK), a water-perfused system with an eight-channel recording capacity13 and an automated pull-through technique. Two resting and two squeeze anal canal pressure readings were obtained from all patients. The recorded data were analysed to determine the mean maximum resting and squeeze anal pressures, reflecting internal and external anal sphincter activity, respectively. Anal canal vector symmetry was derived from the formula originally described by Perry et al.14,15.

Women who had undergone assisted vaginal delivery underwent anal ultrasound to evaluate potential structural damage to the anal sphincters10,16. Endosonography was performed using a 360° ultrasonographic scanner (Bruel & Kjaer, Naerum, Denmark)17 employing a 10-mHz rotating endosonic probe.

Ultrasound procedures were performed by the primary investigator and were supervised by a specialist radiologist, blinded to each patient's history, who subsequently reported the scans.

To assess the effect of normal vaginal delivery on pudendal nerve function, without the possible confounding influences of instrumental delivery10 and possible direct anal sphincter damage, neurophysiology studies were confined to those women who had delivered spontaneously. Studies were performed using a Viking Quest apparatus and needle electrodes (Nicolet Biomed, Madison, Wisconsin, USA). The clitoral–anal reflex18 was assessed by stimulating the paraclitoral area with a prong electrode, while a recording electrode was placed in the external anal sphincter. Both distal latency (normal range 28–50 ms) and sensory threshold (normal range 2.5–6 mA) were recorded19. Needle electromyography was then performed to assess spontaneous activity20, recruitment patterns21 and duration and amplitude of action potentials in the external anal sphincter. All testing was conducted by a clinical neurophysiologist blinded to each patient's history.

The sample size of 178 was calculated to have 80% power to detect a reduction of 50% in the rate of instrumental vaginal delivery in nulliparous women associated with epidural by use of immediate pushing from 40% to 20% (α= 0.05); the hospital's rate of primiparous instrumental delivery varied between 40% and 43% in the three years preceding the study. Statistical analysis was performed with the Yates corrected χ2 test to compare intrapartum and categorical variables. The Mann–Whitney U test was used for comparison of objective test results and duration of labour. These analyses were performed using SPSS for Windows (SPSS, Chicago, Illinois).

Results

A summary flow chart of recruitment and trial participation is shown in Fig. 1. Of the eligible 178 women, 90 (51%) were randomised to immediate pushing and 88 (49%) to delayed pushing. There were no statistical differences between the two groups regarding antenatal and intrapartum variables (Table 1), including oxytocin use. The overall duration of labour was significantly longer in those who delayed pushing (427 vs 480 minutes, P= 0.005), this delay being due to a prolongation in the passive phase of the second stage in the delayed pushing group. Within the immediate pushing group, 13/90 had a second stage which lasted longer than 60 minutes. As there was no passive stage, this was due to prolonged pushing because delivery was considered imminent by the attending midwife. Within the delayed pushing group, all women had total second stages exceeding 60 minutes by virtue of a passive stage of at least 60 minutes, in addition to the duration of active pushing. The durations of oxytocin administration and epidural analgesia both lasted longer in the delayed pushing group with a trend toward significance (Table 2).

Figure 1.

Comparison of the effects of delayed versus immediate pushing with epidural analgesia on mode of delivery and faecal continence—flow chart.

Table 1.  Antenatal/intrapartum variables. Values are given as median (range) or n (%).
 Immediate pushing (n= 90)Delayed pushing (n= 88)
Age28 (18–38)30 (18–40)
Antenatal classes72 (80)76 (86)
Gestation at delivery (days)284286
Spontaneous labour65 (72)55 (63)
Induced labour25 (28)33 (37)
Indications for induction  
Postdates15 (60)20 (61)
Pains6 (24)6 (18)
Fetal reasons4 (16)7 (21)
Oxytocin use76 (84)71 (81)
Duration of labour (minutes)427 (131–827)480 (165–976)
Duration of first stage (minutes)350 (80–827)360 (65–854)
Birthweight (kg/median)3.59 (2.64–4.64)3.52 (2.7–4.7)
Table 2.  Duration of labour, oxytocin use and epidural. Values (minutes) are medians (interquartile ranges). Mann–Whitney U test.
 Immediate pushingDelayed pushingP
  1. * One woman in the immediate pushing group required a caesarean section before active pushing commenced.

Duration of labour427 (131–827)480 (165–976)0.005
Duration of first stage350 (80–827)360 (65–854)0.78
Duration of second stage60 (0–148*)120 (57–225)<0.001
Duration of waiting0 (0–0)60 (25–140)<0.001
Duration pushing60 (0–148*)56 (8–130)0.37
Duration pushing/SVD51 (20–92)46 (8–85)0.14
Duration of epidural300 (101–767)348 (60–856)0.11
Duration of oxytocin199 (24–707)281 (30–860)0.05

Immediate pushing was not accompanied by a significant reduction in the instrumental delivery rate. In the immediate pushing group, 39% underwent an instrumental delivery compared with 44% in the delayed pushing group (Table 3). The converse of this is that a prolonged labour as experienced by those in the delayed pushing group was not beneficial in terms of instrumental delivery reduction. A statistically insignificant increase in failed vacuum/forceps delivery was found in association with delayed pushing; in 1/5 and 2/11 cases of immediate and delayed pushing, respectively, failed vacuum delivery was associated with persistent occipito-posterior position. Five (6%) women in the immediate pushing group and three (4%) in the delayed pushing group underwent caesarean delivery, one because of fetal distress prior to the commencement of pushing and four because of failure to advance in the second stage. Fetal outcome was similar; five infants from the immediate pushing group and six from the delayed pushing group required admission to the neonatal unit; one infant from the immediate pushing group suffered neonatal seizures.

Table 3.  Outcome measures. Values are given as n (%) or median (range).
 ImmediateDelayedPRR (95% CI)
  1. SVD = Spontaneous vaginal delivery.

  2. LSCS = Lower segment caesarean section.

Mode of delivery (n= 90) (n= 88)  
SVD50 (55)46 (52) 1.14 (0.63–2.06)
Forceps12 (13)11 (12.5) 1.08 (0.45–2.59)
Vacuum18 (20)17 (19) 1.04 (0.50–2.19)
Vacuum/forceps5 (5.5)11 (12.5) 0.41 (0.14–1.24)
Caesarean5 (5.5)3 (4) 1.67 (0.39–7.19)
Fetal outcome    
Cord pH (median)7.247.230.75 
Perineum (n= 85) (n= 85)  
Episiotomy66 (73)61 (69) 1.37 (0.68–2.74)
Third degree tear9 (10)6 (7) 1.56 (0.53–4.59)
Second degree tear7 (8)8 (9) 0.86 (0.29–2.50)
Dyspareunia16/82 (20)18/80 (23) 0.83 (0.39–1.78)
Postpartum bowel function (n= 90) (n= 88)  
Symptomatic23 (26)33 (38) 0.57 (0.30–1.08)
Median continence score3 (2–8)4 (1–9)0.27 
Patient satisfaction (n= 90) (n= 88)  
Very happy/SVD again71 (79)67 (76) 1.17 (0.58–2.37)
Unhappy/LSCS next time9 (10)8 (9) 1.11 (0.41–3.02)
Undecided10 (11)13 (15) 0.72 (0.30–1.74)

Nine (10%) women in the immediate and six (7%) in the delayed pushing groups sustained recognised third degree perineal tears, which were repaired as described by Fitzpatrick et al.22. Overall, 23 (26%) women in the immediate pushing group and 33 (38%) in the delayed pushing group experienced alteration of faecal continence postpartum. Faecal urgency of less than 5 minutes was documented in 18 (20%) and 18 (21%) women of the immediate pushing and delayed pushing groups, respectively (Table 3).

There was no statistical difference in results of anal manometry obtained between those women who delayed pushing and those who pushed immediately. Among those women who underwent anal endosonography following an instrumental delivery, findings were abnormal in 21/35 (60%) and 20/39 (51%) of the immediate pushing and delayed pushing groups, respectively. Two women in the immediate pushing group had clinically significant external anal sphincter defects that exceeded one quadrant of the anal canal circumference, which had not been recognised at time of delivery. The remaining 39 women had less extensive external anal sphincter or internal anal sphincter defects. There were no statistical differences between the two groups in respect of endosonographic results (Table 4).

Table 4.  Results of anal manometry in median (range), endoanal ultrasound and neurophysiology in n (%).
 Immediate pushingDelayed pushingPRR (95% CI)
  1. EAS = External anal sphincter.

  2. CAR = Clitoral–anal reflex.

Manometry (mmHg) (n= 90) (n= 88)  
Squeeze pressure93 (11–220)100 (27–174)0.19 
Resting pressure62 (13–138)64 (2–140)0.90 
Squeeze Increment27 (0–131)31 (0–123)0.29 
Vector symmetry index0.67 (0.15–0.90)0.69 (0.14–0.95)0.87 
Ultrasound (n= 35) (n= 39)  
Normal14 (40)19 (49) 0.70 (0.28–1.76)
≤One-quad EAS defect19 (54)20 (51) 1.13 (0.45–2.82)
>One-quad EAS defect2 (6)  0 5.90 (22.6–0.27)
Neurophysiology (n= 42) (n= 41)  
Abnormal EMG5 (12)4 (10) 1.25 (0.31–5.03)
Abnormal CAR10 (24)11 (27) 0.85 (0.32–2.29)

Neurophysiology studies were performed on those women who had undergone spontaneous vaginal delivery. It proved possible to fully assess 42 of the 50 women who had spontaneous delivery in the immediate pushing group and 41 of the 46 women who had spontaneous delivery in the delayed pushing group; in the remaining 13 women, neurophysiology tests were incomplete due to patient discomfort. In total, 15/42 (36%) studies in the immediate pushing group and 15/41 (37%) studies in the delayed pushing group were abnormal. Ten (24%) women in the immediate pushing group and 11 (28%) women in the delayed pushing group showed prolongation of the sensory threshold of the clitoral–anal reflex (>6 mA); no patient in either group had abnormal prolongation of the distal latency of the clitoral–anal reflex. This pattern was consistent with transient demyelination of the pudendal nerve, secondary to compression. Five women in the immediate pushing group and four women in the delayed pushing group had positive sharp waves, increased fibrillation potentials, reduced recruitment patterns and abnormal motor unit action potentials on electromyography, suggesting denervation and ongoing reinnervation within the external anal sphincter. There were no significant differences in neurophysiological results between women in the delayed pushing group who had a passive stage >60 minutes (n= 11) compared with those who had a passive stage 60 minutes or less (n= 30).

When asked about their preferred mode of delivery on subsequent pregnancies, 70% of women in both groups were satisfied with their outcome and would opt for a spontaneous vaginal delivery on a subsequent pregnancy. Ten percent of women in both groups would opt for a caesarean delivery of their next pregnancy; all of these women had undergone an instrumental delivery. The remainder were undecided.

Discussion

The results of this randomised controlled trial show that the instrumental delivery rate following both immediate and delayed pushing was similar, with delayed pushing leading to a significantly longer duration of labour.

Epidural analgesia has become a widely available intervention in many maternity units during the past 20 years. Its benefits in terms of pain relief are undeniable. The effects of epidural analgesia on the progress of labour, mode of delivery and fetal outcome have been widely reported and a number of studies have examined the practise of delaying pushing in the second stage of labour as a means of reducing the increased instrumental rate associated with epidural analgesia; the results, however, are conflicting. While some investigations have shown a reduction in instrumental delivery when pushing is delayed for 60 minutes or more4,23,24, others have shown the contrary6,7,25. Difficulty in interpreting these findings may arise due to a lack of standardisation in labour management that impacts on the overall duration of second stage of labour, length of delay allowed and length of active pushing permitted. This prospective, randomised controlled trial was conducted in a context in which all first labours were managed according to a long established and a clearly defined Active Management protocol11, which standardises the duration of second stage of labour to 2 hours and restricts pushing to 60 minutes; these time limits were occasionally extended in cases where vaginal delivery was imminent or on patient request. Our study has shown that altering the standard management to one of immediate pushing with full dilatation showed no benefit in terms of reduction in the instrumental delivery rate. A shorter labour of 60 minutes would appear to be a benefit although women in our study were not directly questioned concerning this and satisfaction ratings were similar in both groups.

The current practise of delayed pushing in the second stage prolongs labour without any demonstrable benefits to patients. As well as prolonging labour, bed occupancy in the delivery ward was prolonged, emphasising the need to assess carefully any practise prior to its incorporation into common management protocols. Our findings concur with Vause et al.24 that there is little evidence to support a uniform policy of delayed pushing in women with epidural analgesia.

The second objective of our study was to examine the impact of a prolonged second stage on the anal sphincter mechanism, both in terms of neurological function and continence symptoms. A recent investigation26 concluded that there was an increased incidence of perineal trauma associated with epidural anaesthesia, due to more frequent use of episiotomy and operative vaginal delivery. In our study, there were no differences in episiotomy rates, significant perineal trauma or perineal pain in those women who pushed immediately compared with those who delayed pushing. Anal manometry, endoanal ultrasound, neurophysiology studies and symptoms scores were similar in both groups. The study did reveal, however, high overall rates of pudendal nerve damage, anal sphincter injury and altered faecal continence. These findings confirm and reinforce the prevalence of this problem among the parturient population10,16,27.

Neurophysiological assessment of the pelvic floor following spontaneous vaginal delivery revealed no significant differences between the immediate and delayed pushing groups; one-third of women in both groups had evidence of pudendal neuropathy.

The left side was slightly more affected than the right, consistent with findings by Fynes et al.28 and Sultan et al.29. Sensory threshold prolongation is consistent with transient demyelination of the pudendal nerve due to fetal head compression18; prolonging the second stage of labour by 1 hour increases neither the incidence nor the extent of prolongation of the sensory threshold significantly. These findings contradict those of other researchers10,29, although our imposed time limit of a 60-minute second stage delay may account for this disparity, as other studies did not have strict criteria for the length of delay or second stage of labour.

We conclude that neither immediate nor delayed pushing in the presence of epidural analgesia significantly alters the instrumental delivery rate. Delayed pushing significantly increases the duration of labour, but it does not influence postpartum continence, abnormal anal manometry, endoanal ultrasound or pudendal neurophysiology.

Acknowledgements

This study was supported by a grant from the Irish Health Research Board.

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