Summary of main results
We included four randomised controlled trials (involving 388 women) in this review, all of which were conducted prior to 1980, and assessed a variety of different agents and techniques for achieving pain relief during forceps delivery (Ellingson 1977; Hutchins 1980; Mundow 1974; Sagen 1973). Three of the trials compared diazepam with alternative agents (ketamine, vinydan-ether, "other") for the provision of general anaesthesia during forceps delivery, and the fourth trial compared the use of spinal analgesia versus pudendal block (using lignocaine in both groups). No trials assessed the use of epidural analgesia.
Considering the review's primary outcome of pain relief, no significant difference was found when diazepam was compared with ketamine in one small trial (Ellingson 1977). A further trial suggested possible benefit of diazepam compared with vinydan-ether, with women receiving diazepam being significantly more likely to judge pain relief as effective, than women receiving vinydan-ether (Sagen 1973). In a trial comparing spinal analgesia with pudendal nerve block, women receiving spinal analgesia were shown to be significantly more likely to regard the analgesia as adequate and less likely to report severe pain (Hutchins 1980).
None of the trials reported on the review's other two primary outcomes of serious maternal adverse effects or complications, and neonatal mortality and serious morbidity.
No differences were shown between groups in trials assessing the outcomes maternal hypotension (Hutchins 1980), and maternal apnoea requiring oxygen ventilation (Ellingson 1977). In Sagen 1973, women receiving diazepam compared with vinydan-ether, were however significantly less likely to experience vomiting.
No significant differences between groups were seen for the neonatal outcomes Apgar score of less than seven at five minutes (Ellingson 1977; Sagen 1973), and acidosis defined by cord blood arterial pH less than 7.2 (Ellingson 1977) in any of the trials. No further secondary maternal and neonatal outcomes were reported in any of the four included trials.
Some support for diazepam, as compared with vinydan-ether and ketamine, was provided by two of the included trials in relation to non pre-specified review outcomes (Ellingson 1977; Sagen 1973). In the trial comparing diazepam with vinydan-ether, women receiving diazepam were more likely to report feeling comfortable during induction and recovery, and were more likely to have good anaesthesia as judged by the obstetrician (Sagen 1973). As compared with ketamine, women receiving diazepam were more likely to report a pleasant recovery in one trial (Ellingson 1977); interestingly however, in this trial, women receiving diazepam were less likely to have good anaesthesia as judged by the obstetrician.
Three of the four included trials compared diazepam with alternative agents for the provision of general anaesthesia during operative delivery (Ellingson 1977; Mundow 1974; Sagen 1973). The fourth trial compared spinal anaesthesia with pudendal nerve block (Hutchins 1980). The risks, including maternal death, associated with obstetric general anaesthesia have however lead to its use now being restricted predominately to true emergency cases, where there is insufficient time for a regional technique (Djabatey 2009). Accordingly, estimates of use of general anaesthesia during forceps deliveries from current clinical practice are extremely low (estimated to be used in only 0.5% of instrumental births in Australia in 2009 (Li 2011) and in England in 2011 to 2012 (NHS 2012)), and rather regional anaesthesia (particularly epidural or caudal, accounting for over 50%), is the most commonly used method, followed by local anaesthesia to the perineum. While both spinal and pudendal block anaesthesia are used in current clinical practice, they too are used comparatively infrequently (in 2.7% and 5.2% of instrumental birth respectively).
The possible benefits of diazepam shown in two of the included trials when compared with vinydan-ether (Sagen 1973) and ketamine (Ellingson 1977), should be interpreted with caution, and not without acknowledgement of the now known potential dangers of diazepam for obstetric patients (FDA 2008; Grant 2011). While use throughout pregnancy (such when indicated for anxiety) has been suggested to be associated with an increased risk of congential malformations and other developmental abnormalities for the fetus, single high doses during labour and delivery (as used in Ellingson 1977 and Sagen 1973) have been associated with irregularities in fetal heart rate tracing, along with respiratory depression, hypotonia, poor sucking and hypothermia in the neonates (FDA 2008). Indeed, the dose used in both Ellingson 1977 and Sagen 1973 (30 mg intravenously, administered rapidly), was notably high (with recent cited dosing regimens for diazepam analgesia during labour and delivery including 2-5 mg intravenously, and 10 mg intramuscularly (Grant 2011)). For the mother, the risk of aspiration (due to obtunded (dulled/reduced) airway reflexes) is also increased with the use of diazepam during labour and delivery; and as a potent amnesic, the risk of an impaired memory of delivery for the mother is also considered high (Grant 2011).
Forceps deliveries (indicated when the fetus fails to progress to delivery, or when delivery needs to be expedited in the second stage) are no longer considered common; comprising approximately 1% to 4.6% of deliveries in high-resource settings (Li 2011; Martin 2009; Public Health Agency of Canada 2008) and comprising a significantly lower proportion of deliveries in low-resource settings (with for example, an estimation of less than 1% of all births being assisted/instrumental in sub-Saharan Africa) (Bailey 2005). Clinical practice guidelines for instrumental delivery recommend that in preparation of the mother for delivery "appropriate analgesia" should be administered (RANZCOG 2009a; RCOG 2011; SOGC 2004), however, no further guidance as to the particular agent or method to use is provided. For rotational forceps deliveries, such guidelines suggest that regional anaesthesia (either epidural or spinal) should be used (RANZCOG 2009b); yet pudendal block may be appropriate in the context of urgent delivery (RCOG 2011). In Australia and the United Kingdom, it has been estimated that approximately 50% of women undergoing an instrumental delivery will receive regional anaesthesia; and in Australia, approximately 28.4% of women will receive a local anaesthetic to the perineum, and 5.2%, a pudendal block (Li 2011).
Overall completeness and applicability of evidence
There is a significant lack of randomised trials in this area, particularly assessing the techniques and agents commonly used in current clinical practice for the provision of pain relief during forceps delivery.
This review is limited with the inclusion of only four small trials (Ellingson 1977; Hutchins 1980; Mundow 1974; Sagen 1973), that were all conducted prior to 1980, and did not report on many of the review's pre-specified maternal and neonatal primary and secondary outcomes. The variety of analgesic agents/methods used in the four included trials meant that no data could be pooled in meta-analysis, making interpretation difficult. The different methods of measuring pain relief and maternal satisfaction/comfort also made comparisons between trials difficult. One trial (Mundow 1974), reported no data in way that could be included in the review (outcome data were reported for one group only).
Three of the four trials compared diazepam with alternative agents for the provision of general anaesthesia during forceps delivery; this method for providing analgesia during instrumental delivery is however, now infrequently used in clinical practice. The fourth trial compared the use of lignocaine for spinal and pudendal block anaesthesia; while both methods are currently used in practice, they too are employed much less frequently than regional anaesthesia (epidural and caudal), and local anaesthesia to the perineum, which have not been evaluated in any randomised trials of forceps delivery to date.
An important consideration to note, further limiting the applicability of the current evidence, is the now common use of regional, particularly epidural analgesia in modern practice; not a feature of practice at the time the included trials were conducted. Since the introduction of epidural for pain relief approximately four decades ago, the rates of use have increased substantially, with approximately a third of women in labour in the United Kingdom and Australia (Li 2011; NHS 2012), and approximately two thirds of women in labour in the United States now receiving epidural analgesia (McGrady 2004; Osterman 2011). Consideration of this clinical context will be important during the design of any future clinical trials - for example in the setting of high rates of epidural use for pregnant women in labour, an appropriate trial intervention for analgesia for forceps delivery, might be the use of a 'top up' epidural.
Quality of the evidence
All trials were judged to be at a unclear to high risk of bias overall. The four trials were judged at an unclear risk of selection bias with unclear methods for allocation concealment and random number sequence generation (Ellingson 1977; Hutchins 1980; Mundow 1974; Sagen 1973). All four trials were at a high risk of performance and detection bias, with no blinding detailed. One trial was judged at a high risk of bias due to incomplete reporting (Mundow 1974), and two at an unclear risk (Ellingson 1977; Hutchins 1980); only one trial was judged at a low risk of attrition bias (Sagen 1973). Two trials were judged at an unclear risk of reporting bias (Ellingson 1977; Sagen 1973), and two at a high risk (Hutchins 1980; Mundow 1974).
Potential biases in the review process
The evidence for this review is derived from trials identified through a detailed search process. It is possible (but unlikely) that additional trials assessing analgesia for forceps delivery, have been published but not identified. It is also possible that other studies have been conducted but not published. Should such studies be identified we will include them in future updates of this review.
Agreements and disagreements with other studies or reviews
This review confirms that there is currently insufficient evidence to support a particular analgesic agent or method as most effective and safe for providing pain relief during forceps delivery. There have not been other systematic reviews on the use of analgesia for this indication.