Methods	Randomised controlled trial of self-help materials and health education to support women to stop smoking in pregnancy Study conducted in a teaching hospital (academic) clinic in North Carolina, USA from August 1991 to January 1993
Participants	Inclusion criteria: Pregnant women who smoke. Exclusion criteria: > 36 weeks’ gestation, psychiatric diagnosis. Recruitment: 842/846 (99%) women attending the clinic completed survey and 793/846 provided a CO breath sample.; 2 were excluded as > 36 weeks’ gestation; 1 for psychiatric diagnosis; leaving 266 (32%) eligible smokers (smoked at least once in the prior week). 12 refused, 4 were missed, 2 were not pregnant and 1 was a private patient. 247 women randomised Baseline characteristics: Mean cigs/day (C = 14.4, I = 13.5), Want to quit (C = 81%, I = 84%). Smokers in household (C = 75%, I = 78%) White (C = 74%, I = 78%), Single (C = 44%, I = 47%), < 12yrs education (C = 43%, I = 48%) Progress+ coding: Low SES.
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: 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: (i) 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; (ii) given Windsor’s self-directed 7-day smoking cessation guide; (iii) 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; (iv) successful quitters sent an encouraging postcard each week Main intervention strategy: Counselling (multiple intervention) compared to usual care Intensity: Frequency (C = 0, I = 6), Duration (C = 0, I = 2). Usual care intensity: F = 1, D = 1 Intervention provided by existing staff: Effectiveness study
Outcomes	Biochemically validated abstinence at last prenatal visit (late pregnancy*). > 50% reduction in self-reported smoking*; Mean cigarettes per day* Cost-effectiveness data reported.
Notes	SDs for mean cigarettes per day were not reported, therefore we calculated a mean SD from 14 studies with available mean cigarette SDs (6.5) to include in this review, as recommended by the cochrane handbook
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random numbers.
Allocation concealment (selection bias)	High risk	State that neither the enrolling nurse nor the patient were aware of allocation, but experimental group notes were flagged
Incomplete outcome data (attrition bias) All outcomes	High risk	Attrition 40/247 (16%) (4 miscarriages first trimester, 3 miscarriages second trimester, 3 terminations, 15 moved to alternative care, and 12 lost to follow-up) 207 included in analysis (C = 100, I = 107). Those lost to follow-up not able to be re-included in analysis in this review as numbers not reported by study arm
Selective reporting (reporting bias)	Unclear risk	Not apparent.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Exhaled CO measured at each visit for the experimental group and at 3 visits for the comparison group. < 5 ppm counted as non-smokers
Blinding of participants and personnel (performance bias) All outcomes	High risk	Case notes flagged. States patient not aware of randomisation status
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	No significant differences noted.
Contamination of control group	High risk	Concerns about residents having to treat similar/consecutive patients differently, and self-help manuals accidentally given to some controls. Discussion section reports evidence of contamination with self-help materials being given to controls