Donatelle 2000.

Methods	Randomised controlled trial of "Significant Other Supporter" (SOS) program, of social support and direct financial rewards to reduce smoking during pregnancy and postpartum. Study conducted in Oregon WIC program sites, USA, between June 1996 and June 1997.
Participants	Inclusion criteria: Women smoking (even a puff in the last 7 days); less than 28 weeks' gestation; over 15 years of age; literate in English. Exclusion criteria: Not specified. Recruitment: 220/309 (71%) eligible women were randomised (C = 108, I = 112). Baseline characteristics: Mean salivary cotinine at baseline: I = 45.4; C = 45.7. Caucasian (I = 90%, C = 88%), household income < $20000 (I = 87%, C = 89%), Single (I = 47%, C = 42%), Mean age (I = 23.5, C = 24.0). Progress + coding: Low SES.
Interventions	Control: Verbal and written information on the importance of smoking cessation, a pregnancy specific smoking cessation self‐help kit, and monthly telephone calls for self‐reports on their smoking status. Intervention: 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. Main intervention strategy: Incentives (multiple intervention) compared with a less intensive intervention. Intensity: Frequency (C = 2, I = 6), Duration (C = 1, I = 3)‐estimated duration as limited information available. The intervention was delivered by trained program staff or research staff: efficacy study.
Outcomes	Biochemically validated 7‐day point prevalence smoking cessation at 34 weeks' gestation (late pregnancy*) and 2 (0‐5*) months postpartum.
Notes	Data in outcome tables is inconsistent.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided.
Allocation concealment (selection bias)	Unclear risk	No information provided.
Incomplete outcome data (attrition bias) All outcomes	Low risk	High attrition rates I = 32%; C = 51.5% (reasons not specified), but all dropouts included as continuing smokers in this analysis.
Selective reporting (reporting bias)	Low risk	Main outcomes reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	7‐day point prevalence validated by salivary cotinine analysis (> 30 ng/mL considered to be smokers). Salivary thiocyanate also used to confirm non‐smokers for immediate feedback only (> 100 ug/mL considered to be smokers).
Blinding of participants and personnel (performance bias) All outcomes	High risk	Neither providers nor women were blinded for this educational intervention with incentives.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Unclear risk	No process evaluation reported.
Equal baseline characteristics in study arms	Low risk	Preliminary analysis indicates no significant differences exist between randomised groups on baseline demographic characteristics.
Contamination of control group	Low risk	Control group not reported clearly ‐ however intervention given by trained research staff rather than UC providers so unlikely that there was contamination