Methods	RCT.
Participants	70 women in established labour admitted to a hospital in Norway for delivery Inclusion criteria: cervical dilation 4 cm or more, expected to have normal birth, at term after a normal pregnancy
Interventions	Intervention group: TENS to lower back. Comparison group: placebo TENS of identical appearance. Conventional drugs available to both groups.
Outcomes	Women’s views of pain relief and use of other analgesics.
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Not described.
Allocation concealment (selection bias)	High risk	Coin tossed after recruitment to decide group allocation.
Blinding (performance bias and detection bias) Participants	Unclear risk	Placebo device, but not clear whether it was convincing to women and staff
Blinding (performance bias and detection bias) Clinical staff	Unclear risk	Unclear.
Blinding (performance bias and detection bias) Outcome assessor	Unclear risk	Unclear.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent loss to follow up.
Other bias	Unclear risk	Some baseline imbalance between groups with more primiparous women in the intervention group