Jain 1978.

Study characteristics
Methods	Randomised controlled trial Sample size calculation not stated
Participants	Setting: New Orleans, USA. Time of study not stated Inclusion criteria: postpartum women who had an uncomplicated vaginal birth with moderate or severe uterine cramp pain (self‐rated pain score of 60% or more). The women were aged between 16 and 35 years Exclusion criteria: women dependent on analgesics or tranquillisers or hypersensitive to salicylates or caffeine. Women with gastrointestinal, hepatic or renal disease or history of psychiatric illness
Interventions	Following initial pain assessment participants were allocated to 1 of 3 treatment groups and given 1 dose of study medication Aspirin 650 mg (N = 7). Aspirin 800 mg plus caffeine 64 mg (N = 8). Placebo (N = 8).
Outcomes	Pain as measured by the authors: pain was measured on a VAS of 0 (no pain) to 100 (worst pain ever experienced) hourly for 4 hours and reported as a percentage of the score reported before the intervention (0 hours) Maternal adverse events: at the last interview women were asked about side effects
Notes	This study included women with perineal pain and reported the majority of pain assessments including both groups of women Dates of study: not stated Funding sources: blinded drugs supplied by American Home Products. Statistical support from Ives Laboratories and Wyeth Laboratories Declarations of interest: none stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Methods state "patients were separated at random". Insufficient information to permit judgement
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information to permit judgement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information to permit judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data on all women randomised are reported. There were 7 women allocated to the aspirin 650 mg group, and 8 women to each of the aspirin 800 mg and placebo groups. Baseline pain and all reported pain outcomes were included for the 23 women with uterine pain
Selective reporting (reporting bias)	Unclear risk	No published protocol or trial registration
Other bias	Low risk	No other risk of bias identified