Methods	RCT.
Participants	Study in Denmark. 26 women. Inclusion criteria: first birth, expecting normal delivery, no pacemaker, nerve problems, skin problems or psychiatric illness. Cervical dilatation 3 to 5 cm at recruitment
Interventions	Intervention group: TENS to back. Control group: placebo equipment (with flashing lights but no current)
Outcomes	Other analgesics used.
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated.
Allocation concealment (selection bias)	Unclear risk	Not stated.
Blinding (performance bias and detection bias) Participants	Unclear risk	Placebo device provided.
Blinding (performance bias and detection bias) Clinical staff	Unclear risk	Placebo device provided; unclear whether it was convincing to staff
Blinding (performance bias and detection bias) Outcome assessor	Unclear risk	Placebo device provided; unclear whether it was convincing to staff
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear.
Other bias	Unclear risk	Unclear.