Ho 1993

Methods	Women 'randomly allocated' to 2 groups. A random number table used to generate the allocation sequence and allocation was done by sealed envelopes. Placebos were not used. Side effects were recorded by women
Participants	880 healthy women attending Family Planning Association clinics in Hong Kong Included women with regular menstrual periods (21‐35 days), aged 18‐45 years, with a single act of unprotected intercourse within 48 h of attending the clinic
Interventions	Yuzpe (ethinyl oestradiol 100 μg + norgestrel 1 mg, repeated after 12 h) vs LNG 0.75 mg, orally, 2 doses 12 h apart
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	Observed pregnancy/expected pregnancy/total number of women: Yuzpe 15/22/424; LNG 12/20/410 Loss to follow‐up: Yuzpe 16/440 (3.6%); LNG 30/440 (6.8%)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Women were 'randomly allocated' into 2 groups ‐ doesn't state how
Allocation concealment (selection bias)	Unclear risk	Method of concealment not stated
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Blinding not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reported loss to follow‐up‐ "Of these, 16 subjects in the Yuzpe group and 30 subjects in the levonorgestrel group were lost to follow up after the first visit and the results of treatment were not known. These subjects were excluded from the analysis."
Selective reporting (reporting bias)	Low risk	Planned outcomes were reported
Other bias	Low risk	None detected