Webb 1992.

Methods	Women 'randomly allocated' to 3 groups. Random number generation by computer. Schedule prepared by someone not involved in recruitment and outcome assessment. No blinding or use of placebos reported. Side effects were recorded by women
Participants	616 healthy women attending a community family planning clinic in Liverpool, UK Included women with regular menstrual periods (21‐35 days), aged 16‐45 years, with attended the clinic within 72 h of a single act of unprotected intercourse
Interventions	Yuzpe (ethinyl oestradiol 100 μg + norgestrel 1 mg, repeated after 12 h) vs danazol 600 mg, twice, 12 h apart vs Mife 600 mg, single dose
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	Loss to follow‐up: 27/616 (4.4%). Pregnancy outcome assessed in 94%, side effects in 94%, menstrual changes in 92% of women Trial stopped after recruitment of 616 of the 1200 initially targeted because of differences in efficacy in an interim analysis Observed pregnancy/expected pregnancy/total number of women: Yuzpe: 5/11/191; danazol: 9/12/193; Mife 0/12/195
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The allocation sequence was constructed by using a computer based pseudo‐random number generator with a uniform distribution."
Allocation concealment (selection bias)	Unclear risk	"The schedule was prepared before the start of the study by JR, who did not participate in either the selection or assessment of women." No mention of method of concealment so unclear
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No mention of blinding or placebo reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Attempts to explain loss to follow‐up but the numbers actually analysed don't add up to those remaining
Selective reporting (reporting bias)	Low risk	Planned outcomes were reported
Other bias	Low risk	None detected