Davies 1982.

Study characteristics
Methods	Randomised controlled study, UK.
Participants	35 women who were delivered by elective CS under general or epidural anaesthesia received TENS active or control (18 general anaesthesia: control 8 and TENS 10; 17 epidural analgesia: control 6 and TENS 11). The intervention group n: 22 and the control group n: 14.
Interventions	All participants received conventional analgesia (15 mg of papaveretum intramuscularly or Distalgesie 2 tablets‐ paracetamol 650 mg, dextropropoxphene 65 mg); the intervention group received in addition the TENS active, 25 Hz, 200 ms, 0‐40V, intervals of 15 minutes for 24 hours.
Outcomes	Pain scores (linear analogue scale) and the analgesic requirement 24 hours after finalised surgery.
Notes	Funding sources: not mentioned. Setting: UK, no details. Conflicts of interest: not mentioned. Dates of trial: none mentioned, published 1982.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The participants were randomised by a table of random numbers.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The control groups received the stimulator unit without batteries.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not described.
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were no losses.
Selective reporting (reporting bias)	Low risk	Presents the results of the proposed analysis methods.
Other bias	Low risk	We do not suspect any other bias related to this study.