Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	165 women with primary dysmenorrhoea 2 RCTs in this analysis	Proportion of people who experienced any adverse effect 44/87 (51%) with combined oral contraceptives 36/78 (46%) with placebo or no treatment	OR 1.45 95% CI 0.71 to 2.94		Not significant
RCT	115 women with primary dysmenorrhoea	Irregular uterine bleeding 63.2% with low-dose combined oral contraceptive pill (ethinyl estradiol plus norethisterone) 14.5% with placebo Absolute numbers not reported	Reported as significant difference P value not reported	Effect size not calculated	placebo
RCT	115 women with primary dysmenorrhoea	Nausea 14% with low-dose combined oral contraceptive pill (ethinyl estradiol plus norethisterone) 0% with placebo Absolute numbers not reported	Reported as significant difference P value not reported	Effect size not calculated	placebo
RCT	115 women with primary dysmenorrhoea	Total adverse effects 80.7% with low-dose combined oral contraceptive pill (ethinyl estradiol plus norethisterone) 40.0% with placebo Absolute numbers not reported	Reported as significant difference P value not reported	Effect size not calculated	placebo