Olsen 2007.

Study characteristics
Methods	Randomised controlled trial
Participants	Setting: single‐centre study at the Sahlgrenska University Hospital, Gothenburg, Sweden during 2004 Inclusion criteria: 22 women following uncomplicated vaginal birth and painful postpartum uterine contractions requiring pain relief Exclusion criteria: women with systemic disorders; abnormal pregnancy; operative delivery and receiving analgesic treatment for other pain; Swedish as 2nd language
Interventions	Women were randomly allocated to 1 of 2 treatment groups: HI TENS (50 mA for 1 minute, repeated up to 2 times if pain not relieved) (N = 13) LI TENS (10 ‐ 15 mA, repeated up to 2 times if pain not relieved) (N = 8) In both groups the TENS electrodes were placed over the lower part of the abdomen bilaterally over the uterus
Outcomes	Adequate pain relief as reported by the woman: women were asked to estimate their pain intensity using a 100 mm VAS ranging from no pain to worst possible pain, before and after treatment Women in both groups rated the discomfort of treatment using a 5‐point verbal scale from no discomfort to worst possible discomfort. To clarify the difference between the 2 components, women were informed that they should rate both how painful the postpartum uterine contractions were and how unpleasant they thought the contractions were Maternal adverse events: all possible adverse events were recorded
Notes	Dates of study: women recruited in 2004 Funding sources: not stated Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Women were randomised using a "computer generated random table"
Allocation concealment (selection bias)	Low risk	Quote: "Groups coded and transferred to pre‐sealed opaque envelopes"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not possible to blind study personnel
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were 13 women allocated to the HI TENS group and 8 women to the LI TENS group. The data from 1 of 13 women (8%) in 1 allocated to the HI TENS intervention group was excluded because she withdrew after experiencing discomfort
Selective reporting (reporting bias)	Unclear risk	No published protocol or trial registration available
Other bias	High risk	Baseline imbalance ‐ numbers in abstract differ from those given in results