Wu 1999a

Methods	Double‐blind, randomised trial. Random number generation done centrally. Double‐blinded by use of identical placebos. Allocation concealment achieved by sealed, sequentially numbered, tinted bottles filled and labelled by the manufacturer
Participants	1324 women in 16 urban family planning clinics in China Included only women who came within 72 h of unprotected intercourse Excluded women with irregular menstrual periods, with multiple acts of intercourse, on oral contraceptives and post‐abortal women whose menstrual periods had not returned to normal
Interventions	LNG 0.75 mg, 2 doses, 12 h apart vs Mife 10 mg, single dose
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	20 women excluded altogether (reasons not stated) Loss to follow‐up 28 (2.1%) in the 2 groups Observed pregnancy/expected pregnancy/total number of women: LNG 20/49/643; Mife 9/44/633
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number generation done centrally
Allocation concealment (selection bias)	Low risk	Allocation concealment achieved by sealed, sequentially numbered, tinted bottles filled and labelled by the manufacturer
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐blind
Incomplete outcome data (attrition bias) All outcomes	Low risk	Post‐randomisation exclusion and loss to follow‐up reported
Selective reporting (reporting bias)	Low risk	Reported planned outcomes
Other bias	Low risk	None detected