He 2002

Methods	Randomised, double‐blind, multicentre trial. Random number generation done centrally, double‐blinded by use of identical placebos
Participants	400 healthy women recruited into study from family planning clinics in Shanghai, China Included women with regular menstrual periods (24‐42 days), who had a single act of unprotected intercourse within 120 h of attending the clinic, and they were willing to avoid further acts of unprotected coitus during that cycle and willing to have an induced abortion if pregnancy was diagnosed following intake of the study drug during the study period Excluded women: current pregnancy or breastfeeding, on hormonal contraception in the current cycle and those with uncertain dates of last menstrual period and no contraindication to use of Mife or tamoxifen
Interventions	Mife (single dose) 10 mg + placebo vs Mife 10 mg + tamoxifen 20 mg
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	Loss to follow‐up: Mife + placebo 2/200; Mife + tamoxifen 3/200 Observed pregnancy/total number of women: Mife + placebo 3/200; Mife + tamoxifen 1/200
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The subjects were allocated randomly to one of the two treatment groups using a computer‐generated random number table".
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not reported
Blinding (performance bias and detection bias) All outcomes	Low risk	"Neither the participants nor the investigator knew which treatment was received. The tablets of mifepristone and placebo or tamoxifen were swallowed in the presence of a member of the study team who could record the date and time when they were taken." "Double blinded"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Explained loss to follow‐up
Selective reporting (reporting bias)	Low risk	Reported planned outcomes
Other bias	Low risk	None detected