Methods	RCT.
Participants	40 women attending a Boston (USA) hospital. Inclusion criteria: women in active, spontaneous labour with singleton, vertex, term pregnancy, requesting epidural. Cervical dilatation less than 5 cm on recruitment
Interventions	All women had a Bupivacaine epidural. Intervention: TENS to lower back. Comparison Group: placebo/inactive TENS.
Outcomes	VAS pain scores, use of oxytocin, fetal heart rate, Apgar scores and maternal side effects
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided.
Allocation concealment (selection bias)	Low risk	“Sequentially numbered, opaque, shuffled envelopes”.
Blinding (performance bias and detection bias) Participants	Unclear risk	Described as double-blind trial. TENS machines were in pouches so women could not see if they were on or off
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	All women included in the analysis.
Other bias	Unclear risk	Some baseline differences, 7/20 women in the intervention group and 3/20 in the control group had opiate analgesia before entry to the study