Dada 2010

Methods	Women were randomly allocated to 2 groups.  Method of randomisation of double‐blind trial was mentioned in the paper
Participants	3022 Nigerian women with regular menstrual cycles (24–42 days' duration with variation of no more than 5 days) Desired EC within 120 h after a single act of unprotected coitus during the present menstrual cycle, agreed to abstain from further acts of intercourse during that cycle or to use a condom or diaphragm if this was not possible Available for follow‐up over the next 6 weeks
Interventions	2‐dose LNG: participants received 2 doses of LNG 0.75 mg administered 12 h apart Single‐dose LNG: participants received 1 dose of LNG 1.5 mg and 1 LNG placebo 12 h apart
Outcomes	Observed number of pregnancies, side effects and changes in menstrual pattern
Notes	Randomisation sequence computer‐generated by WHO in fixed blocks of 8  Loss to follow‐up: 2‐dose LNG 103/1512; single‐dose LNG: 96/1510 Observed pregnancy/expected pregnancy/total number of women: 2‐dose LNG: 8/165.8/1409; single‐dose LNG: 9/169.1/1414 Side effects:  Nausea: 2‐dose LNG: 332/1512; single‐dose LNG: 328/1510 Vomiting: 2‐dose LNG: 132/1512; single‐dose LNG: 137/1510 Fatigue: 2‐dose LNG: 188/1512; single‐dose LNG: 189/1510 Headache: 2‐dose LNG: 175/1512; single‐dose LNG: 181/1510 Dizziness: 2‐dose LNG: 153/1512; single‐dose LNG: 130/1510
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Allocation to study group (two dose or single dose) was determined through a random‐number sequence, which was computer generated by WHO in fixed blocks of eight."
Allocation concealment (selection bias)	Low risk	"A sealed bag containing the polyethylene bags (of treatment) was labelled with the name of the center, participant number and tablet expiration date. The sealed bags were used sequentially in the order of subject numbers. The allocation sequence was concealed from investigators and WHO staff in Geneva."
Blinding (performance bias and detection bias) All outcomes	Low risk	"Double blinding was maintained throughout for the participants, trial clinicians and outcome evaluators." "Levonorgestrel tablets and levonorgestrel placebo were provided" ; placebo used
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Did not use ITT analysis however still compared baseline characteristics for all women including those lost to follow‐up whereas pregnancy rate analysis used a different sample size
Selective reporting (reporting bias)	Low risk	Reports planned outcomes
Other bias	Low risk	None detected