Cao 1999

Methods	Women 'randomly allocated' to 4 groups. Method of randomisation not reported
Participants	543 women (aged 18‐47 years old) attending the outpatient clinic of the No. 477 Military Hospital, China. Women had regular menstrual periods and unprotected intercourse within 72 h of attending the clinic
Interventions	Mife (single dose) 100 mg vs Mife 50 mg vs Mife 25 mg vs Mife 10 mg, orally
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	No mention of post‐randomisation exclusion and loss to follow‐up Observed pregnancy/expected pregnancy/total number of women: Mife 100 mg 0/13/120; Mife 50 mg 0/16/147; Mife 25 mg 2/14/136; Mife 10 mg 8/14/140
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Mentioned randomisation but description not adequate
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not mentioned
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Any losses to follow‐up or exclusion were not reported
Selective reporting (reporting bias)	Low risk	Planned outcome of pregnancy rate was reported
Other bias	Low risk	None detected