Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Pain
Systematic review	486 women with primary dysmenorrhoea 8 RCTs in this analysis	Proportion of women with at least moderate pain relief with aspirin (650 mg four times daily) with placebo Absolute results not reported	RR 1.60 95% CI 1.12 to 2.29 NNT 10 95% CI 5 to 50	Small effect size	aspirin
Need for additional medication
Systematic review	205 women with primary dysmenorrhoea 3 RCTs in this analysis	Need for additional medication with aspirin (650 mg four times daily) with placebo Absolute results not reported	RR 0.79 95% CI 0.58 to 1.08		Not significant
Systematic review	36 women Data from 1 RCT	Need for additional medication 12/24 (50%) with aspirin (650 mg/day during menses) 7/12 (58%) with placebo	RR 0.86 95% CI 0.46 to 1.60		Not significant