Early versus late epidural analgesia and the risk of instrumental delivery in nulliparous women


Authors’ Reply


We appreciate the critical feedback from Michael Klein1 on our recently published systematic review: Early versus late epidural analgesia and risk on instrumental delivery in nulliparous women: a systematic review.2

However, we do not agree with his comments. Dr Klein suggests that the meta-analysis is primarily about caesarean section, and that the title is therefore misleading. The primary focus of our meta-analysis was the effect of early epidural analgesia (EA) on the rate of instrumental vaginal delivery or caesarean delivery. Table 3 illustrated the inclusion of six studies (15 399 women) for the rate of instrumental delivery and five studies (14 836 women) for the rate of caesarean delivery. Thus, we disagree with Klein’s conclusion, and consider the title appropriate.

The fact that Luxman’s3 study was underpowered is irrelevant because the results were pooled with results from other studies. In addition, Klein refers repeatedly to the fact that there is a low caesarean section rate in several studies. He does not argue, however, about what would be the effect of a higher, versus lower, rate of caesarean section on the relative risk. Looking at relative risks for different studies included in the meta-analysis, we see no link between the rate of caesarean section and the relative risk. Three studies with a caesarean section rate of less than 20% described relative risks of 0.67,3 0.86,4 and 1.16,5 respectively, and two studies with caesarean rates over 20% reported relative risks of 1.026 and 1.05,7 respectively.

After the first request for analgesia, Wong et al.7 randomised women to receive intrathecal fentanyl or systemic hydromorphone. Subsequently, patient-controlled epidural analgesia was initiated in the intrathecal group at the second request, and in the systemic group at a cervical dilatation of at least 4 cm or at the third request for analgesia.

In Wang’s study, a minimum of 1-cm dilation was required to receive epidural analgesia in the early group, and results were compared with the late group in which dilation was at least 4 cm.6 We believe that Klein’s comment on the type of comparison in this study was unjustified.

Finally, Dr Klein expressed doubts about the external validity of Wang’s study to women in spontaneous labour. We, however, see no important difference between the outcomes of studies with spontaneous or induced labour.