Methods	Trial of medical smoking cessation counselling and peer support, in a teaching hospital (academic) clinic in North Carolina, USA. 1991-1993
Participants	All women receiving prenatal care at the University of North Carolina residents clinic were surveyed: 842/846 completed survey; 793/846 provided a carbon monoxide breath sample; 2 were excluded as > 36 weeks’ gestation; 1 for psychiatric diagnosis; leaving 266 eligible smokers (smoked at least once in the prior week) of whom 12 refused, 4 were missed, 2 were not pregnant and 1 was a private patient; 247 recruited, losses were 40 (−4 miscarriage first trimester, −3 miscarriage second trimester, −3 terminations, −15 moved to alternative care, −12 lost to follow up) leaving 107 intervention and 100 control
Interventions	All 1-4 year residents given didactic and role play training for smoking cessation counselling, including self-assessment of current techniques and skills, which they were asked to continue with for the control group. Control group: standard care; residents reminded not to alter amount or time of this; help was provided if woman sought it and prenatal classes included discussion of substance abuse including cigarettes. Intervention: residents provided counselling at each visit, and a brief script aimed at setting a quit date or negotiated an alternative assignment such as a smoking diary at every contact; given Windsor’s self-directed 7 day smoking cessation guide; quit date patients given written prescription to quit, letter of support from doctor, contacted by volunteer smoking cessation counsellor to review the quit plan and encourage follow-through charts flagged, prompts with flow sheet, most recent CO and self-report included for care provider; successful quitters sent an encouraging postcard each week Theoretical basis: feedback and reinforcement. Intensity rating: I = 4, C = 2 (not clear)
Outcomes	Smoking cessation biochemically validated by exhaled CO at each visit. Proportion > 50% reduction in CO
Notes	Concerns about residents having to treat similar/consecutive patients differently, and self-help manuals accidentally given to some controls
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Yes	Computer-generated random numbers.
Allocation concealment?	No	State that neither the enrolling nurse nor the patient were aware of allocation, but experimental group notes were flagged
Blinding? Women and clinical staff	No	Case notes flagged. States patient not aware of randomisation status
Incomplete outcome data addressed? All outcomes	No	Attrition 16%. Drop-outs not reported by intervention group so not able to be included in analysis
Free of selective reporting?	Unclear	Not apparent.
Free of detection bias?	Yes	Expired CO measured at each visit for the experimental group and at 3 visits for the comparison group