Bloomfield 1978.

Study characteristics
Methods	Randomised controlled trial.
Participants	Setting: single centre study at Cincinnati General Hospital ‐ time frame not given Inclusion criteria: women who had given birth within the previous 48 hours with moderate or severe uterine cramp pain as assessed by the woman Women were 18 years or older Exclusion criteria: women experiencing episiotomy pain greater than their uterine cramp pain; unmarried women less than 18 years of age; women with history of aspirin allergy; women given analgesics, sedatives or other psychotropic within previous 6 hours; women breastfeeding their babies
Interventions	Following initial pain assessment women were randomly allocated to 1 of 2 treatment groups, stratified by initial pain intensity, moderate or severe, and given a single dose of 1 of 2 study medications when required. Aspirin 650 mg (2 capsules aspirin 325 mg) (N = 20). Placebo (2 capsules ‐unknown composition) (N = 20).
Outcomes	Adequate pain relief as assessed by the woman: pain was assessed at ½ hour post‐study medication then hourly for 7 hours. All interviews were conducted by the same trained nurse observer Pain intensity measured on an ordinal scale from no pain (0), mild pain (1), medium pain (2) or severe pain (3). Pain intensity difference scores were calculated by subtracting baseline pain intensity scores from pain intensity scores at observed time points. Reported SPID scores were used to calculate 'adequate pain relief as assessed by the woman' (estimated over 7 hours) Women were asked to rate pain relief at the 3rd hour as greater than 50% or not Need for additional analgesia: women requiring greater pain relief were removed from the study and given medication as needed, they were not interviewed further. Data for these women were included in the analysis. Maternal adverse events: women were asked about side effects with minimal use of leading question and without use of a checklist at the final interview. Vital signs including arterial pressure, pulse and respiratory rates and oral temperature were obtained before and 1, 2 and 7 hours after drug administration.
Notes	Additional study arms: this study included an additional 3 arms of fendosal 100 mg, 200 mg and 400 mg. This medication is no longer available, so these arms were not included Dates of study: not stated Funding sources: study funded in part by grant from pharmaceutical company Hoechst‐Roussel Declarations of interest: no declaration of interests statement
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomly assigned using a "predetermined balanced schedule, stratified by pretreatment pain intensity". Unclear exactly how random sequence was generated
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The study was "double blind". "All capsules were identical in taste and appearance."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data from all women randomised were included in analyses. There were 20 women allocated to each group. There were 2 women who required additional analgesia, 1 woman from each group, placebo and aspirin. These women were withdrawn from the study and were not interviewed about pain following withdrawal. Subsequent pain intensity scores were adjusted to their pretreatment score and used in the analysis
Selective reporting (reporting bias)	Unclear risk	No protocol published or trial registration available
Other bias	Low risk	No other risks of bias identified