Bloomfield 1986c.

Study characteristics
Methods	RCT Setting: USA
Participants	203 women with moderate or severe postpartum uterine cramps Number per group not reported Inclusion/exclusion criteria not reported
Interventions	Intervention: single oral dose 650 mg aspirin Intervention: single oral dose 1000 mg acetaminophen  Comparator: placebo
Outcomes	Pain relief and pain intensity
Notes	No useable data. No outcome data presented by intervention group Dates of study: not reported Funding sources: not reported Declarations of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	not reported ‐ "stratified, randomized, double‐blind design"
Allocation concealment (selection bias)	Unclear risk	not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	no information reported on numbers providing data
Selective reporting (reporting bias)	Unclear risk	No protocol, no outcome data presented by group
Other bias	Low risk	Nothing to indicate any other source of bias