Methods	Trial of “Significant Other Supporter” (SOS) program, of bolstered social support and direct financial rewards, for low-income high-risk women in 4 Oregon WIC program sites, US. Conducted between June 1996 and June 1997
Participants	Women smoking (even a puff in the last 7 days); less than 28 weeks’ gestation; over 15 years of age; literate in English. Participation rate 71%. Mean salivary cotinine at baseline: I: 45.4 (n = 112); C: 45.7 (n = 108).
Interventions	Control group received verbal and written information on the importance of smoking cessation, a pregnancy specific smoking cessation self-help kit, and were telephoned monthly for self-reports on their smoking status. The intervention group received as for the control group plus were asked to designate a social supporter (preferably a female non-smoker), and were advised both she and her supporter would receive an incentive: participants were given $50 voucher for each month biochemically confirmed as quit. Supporter received $50 voucher in first month and at 2 months postpartum, and $25 voucher for other months. The intervention was delivered by trained program staff or research staff. Theoretical basis: rewards and social support. Intensity rating: I = 4, C = 3
Outcomes	Smoking cessation biochemically validated with salivary cotinine at 34 weeks’ gestation and 2 months postpartum
Notes	Data in outcome tables is inconsistent.
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	No information provided.
Allocation concealment?	Unclear	No information provided.
Blinding? Women and clinical staff	No	Neither providers nor women were blinded for this educational intervention with incentives
Incomplete outcome data addressed? All outcomes	Unclear	High attrition rates I = 32%; C = 51.5%, but drop-outs included as smokers in this analysis. Those lost to follow up were considered to be smokers
Free of selective reporting?	Yes	Main outcomes reported.
Free of detection bias?	Yes	Reported quitting validated by salivary cotinine analysis.