Comparison 1. TENS versus placebo TENS or routine care.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Severe pain (various definitions) measured in labour	4		Risk Ratio (M-H, Random, 95% CI)	Subtotals only
1.1 TENS to back	2	147	Risk Ratio (M-H, Random, 95% CI)	0.67 [0.32, 1.40]
1.2 TENS to acu-points	2	190	Risk Ratio (M-H, Random, 95% CI)	0.41 [0.31, 0.54]
2 Mean pain score in labour (measured on various VASs)	2	299	Std. Mean Difference (IV, Random, 95% CI)	−1.01 [−1.00, 0.97]
2.1 TENS to back	2	299	Std. Mean Difference (IV, Random, 95% CI)	−1.01 [−1.00, 0.97]
3 Women satisfied with pain relief (various definitions)	6		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
3.1 TENS to back	5	452	Risk Ratio (M-H, Fixed, 95% CI)	1.25 [0.98, 1.60]
3.2 TENS to acu-points	1	90	Risk Ratio (M-H, Fixed, 95% CI)	4.1 [1.81, 9.29]
4 Women would use TENS again in a future labour	5		Risk Ratio (M-H, Random, 95% CI)	Subtotals only
4.1 TENS to back	4	583	Risk Ratio (M-H, Random, 95% CI)	1.50 [1.23, 1.83]
4.2 TENS to acu-points	1	100	Risk Ratio (M-H, Random, 95% CI)	1.45 [1.18, 1.79]
5 Caesarean section rate	10		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
5.1 TENS to back	8	868	Risk Ratio (M-H, Fixed, 95% CI)	1.35 [0.84, 2.17]
5.2 TENS to acu-points	1	100	Risk Ratio (M-H, Fixed, 95% CI)	1.5 [0.26, 8.60]
5.3 Limoge current to cranium	1	20	Risk Ratio (M-H, Fixed, 95% CI)	1.0 [0.07, 13.87]
6 Assisted delivery	9		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
6.1 TENS to back	7	840	Risk Ratio (M-H, Fixed, 95% CI)	0.82 [0.56, 1.19]
6.2 TENS to acu-points	1	100	Risk Ratio (M-H, Fixed, 95% CI)	4.5 [1.02, 19.79]
6.3 Limoge current to cranium	1	20	Risk Ratio (M-H, Fixed, 95% CI)	0.67 [0.14, 3.17]
7 Other pharmacological pain relief required (various definitions)	6		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
7.1 TENS to back	5	358	Risk Ratio (M-H, Fixed, 95% CI)	0.88 [0.76, 1.01]
7.2 Limoge current to cranium	1	20	Risk Ratio (M-H, Fixed, 95% CI)	7.0 [0.41, 120.16]
8 Amount of other medication (various drugs)	2	282	Std. Mean Difference (IV, Fixed, 95% CI)	−0.09 [−0.33, 0.14]
8.1 TENS to back	2	282	Std. Mean Difference (IV, Fixed, 95% CI)	−0.09 [−0.33, 0.14]
9 Augmentation of labour	3		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
9.1 TENs to back	1	94	Risk Ratio (M-H, Fixed, 95% CI)	0.86 [0.59, 1.25]
9.2 TENS to acu-points	1	100	Risk Ratio (M-H, Fixed, 95% CI)	0.93 [0.78, 1.11]
9.3 Limoge current to cranium	1	20	Risk Ratio (M-H, Fixed, 95% CI)	0.56 [0.29, 1.07]
10 Duration of first stage of labour in minutes (various starting points)	5		Mean Difference (IV, Random, 95% CI)	Subtotals only
10.1 TENS to back	3	318	Mean Difference (IV, Random, 95% CI)	−14.10 [−36.73, 8.53]
10.2 TENS to acu-points	2	190	Mean Difference (IV, Random, 95% CI)	−55.77 [−170.30, 58.76]
11 Duration of second stage of labour in minutes	4		Mean Difference (IV, Random, 95% CI)	Subtotals only
11.1 TENS to back	3	318	Mean Difference (IV, Random, 95% CI)	0.59 [−12.21, 13.39]
11.2 TENS to acu-points	1	95	Mean Difference (IV, Random, 95% CI)	−3.0 [−14.87, 8.87]
12 Epidural required	7		Risk Ratio (M-H, Random, 95% CI)	Subtotals only
12.1 TENs to back	5	571	Risk Ratio (M-H, Random, 95% CI)	0.99 [0.59, 1.67]
12.2 TENS to acu-points	1	100	Risk Ratio (M-H, Random, 95% CI)	0.40 [0.08, 1.97]
12.3 Limoge current to cranium	1	20	Risk Ratio (M-H, Random, 95% CI)	0.11 [0.02, 0.72]
13 Fetal distress	2		Risk Ratio (M-H, Fixed, 95% CI)	Subtotals only
13.1 TENS to back	1	200	Risk Ratio (M-H, Fixed, 95% CI)	0.33 [0.01, 8.09]
13.2 TENS to acu-points	1	100	Risk Ratio (M-H, Fixed, 95% CI)	1.0 [0.06, 15.55]