Sang 1999

Methods	Single‐blind randomised trial. Power calculation reported
Participants	2400 women attending urban hospital and family planning clinics in 5 cities in China Included only women who came after 24 h to 96 h of unprotected intercourse Excluded women who had irregular menstrual periods, multiple acts of intercourse, who had been using other oral contraceptives and whose normal menses had not resumed after an abortion or delivery
Interventions	Mife 25 mg vs Mife 25 mg + anordrin 7.5 mg vs Mife 10 mg + anordrin 5 mg vs Mife 10 mg
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	Post‐randomisation exclusions: 2 women Loss to follow‐up: total of 13 cases (0.5%): Mife 25 mg 1; Mife 25 mg + anordrin 7.5 mg 5; Mife 10 mg + anordrin 5 mg 6; Mife 10 mg 1 Observed pregnancy/expected pregnancy/total number of women: Mife 25 mg 10/42/599; Mife 25 mg + anordrin 7.5 mg 9/47.5/595; Mife 10 mg + anordrin 5 mg 7/42.6/594; Mife 10 mg 17/39.7/599 1 ectopic pregnancy in Mife 10 mg group
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	Low risk	Single‐blind
Incomplete outcome data (attrition bias) All outcomes	Low risk	Post‐randomisation exclusions and loss to follow‐up reported
Selective reporting (reporting bias)	Low risk	Reported planned outcomes
Other bias	Low risk	None detected