There are some differences between the published Cochrane protocol for this review (Simmons 2009) and this full review:

John A Crowhurst has left the review team. Matthew G Richardson and Matthew R Bright have joined the review team.

We identified additional trials from ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP), using the search terms as outlined in Appendix 1, as well as searching the reference lists of retrieved studies.

We updated the Methods in line with the standard methods of Cochrane Pregnancy and Childbirth.

The original protocol did not include consideration of cluster‐randomised controlled trials. With the passage of time to the full review, we acknowledged that this study design has become somewhat more prevalent and we therefore included it, with such studies to be analysed according to the methods as described. We found no such studies.

We changed 'Types of participants' from 'Women having an elective caesarean section' in the protocol to 'Women having a caesarean'. We anticipated that included studies were likely to be conducted in an elective setting only. This change allowed for the inclusion of studies involving emergency caesareans as well, this being a common and important participant subgroup, which there was no reasonable basis to preclude.

We have stated in the full review that quasi‐RCTs are not being included.

In the protocol we distinguished between low‐dose and high‐dose spinals without providing any definition. We now provide a definition for 'low dose' in the full review.

The primary outcomes originally stated in the protocol were amended slightly for the full review, with a view to providing greater detail and clarity about important clinical endpoints as follows.

1. 'Number of women requiring an additional intervention for anaesthesia at any time after CSE or spinal anaesthetic insertion' in the protocol was changed to 'Number of women requiring a repeat regional block or a general anaesthetic as a result of failure to establish adequate initial blockade'. This change provided greater detail about the type of additional intervention that may have been needed, and specifically in relation to the occurrence of failure of the regional block at the time of insertion, as opposed to at any time during the operation.

2. We added a new outcome to this review in the form of 'Number of women requiring supplemental intra‐operative analgesia at any time after combined spinal‐epidural or spinal anaesthetic insertion'. We included this to provide specific information about the need for supplementation, which is a lesser intervention than completely redoing the regional block or administering a general anaesthesia.

3. We amended 'Number of women requiring conversion to general anaesthesia' in the protocol to 'Number of women requiring intra‐operative conversion to general anaesthesia' to identify those women who experienced a block failure at any time during the procedure after the initial block establishment, such as for example with prolonged surgery, in which circumstance the use of a CSE could provide rescue not available with a single‐shot spinal.

For the full review we deleted the secondary outcome of 'Women fully breastfeeding at hospital discharge'. In recognising the importance to consumers of this outcome, we had included it in the protocol, but we acknowledged in undertaking the full review that this was unlikely to be significantly influenced by the interventions in this study. Future reviews may include a measure of the timeliness or the number of women able to initiate skin‐to‐skin contact intra‐operatively as being more directly determined by the mode of anaesthesia, especially for complications and failure rates.

For the full review we amended the secondary outcome 'Number of women with an intra‐operative complication requiring treatment or intervention specifically identified: pruritus, nausea and/or vomiting, hypotension, respiratory depression/arrest, sedation, high block' to the specific adverse events considered individually: 'Number of women with hypotension', 'Number of women with nausea and or vomiting', and 'Number of women with a post‐dural puncture headache'. This was to avoid potential confusion that may have arisen from this being seen as an aggregate measure versus each type of event being counted separately.

This review also excluded two studies Gurlit 2003 and Mueller 2010. Both of these studies compared SSS and CSE for caesarean section and only evaluated post‐operative pain relief, which was not relevant for our review.