Methods	Randomised controlled study of health education and feedback to support women to stop smoking Location and study dates unclear. Assume USA due to author affiliations
Participants	Inclusion criteria: Women enrolling for prenatal care. Exclusion criteria: Not further specified. Recruitment: 49 women randomised (I = 26, C = 23). Baseline characteristics: Not reported (abstract only).
Interventions	Control: Usual prenatal care. Intervention: Education and at least 8 encounters with a program counsellor. Peak flow values and CO levels were obtained at each prenatal visit and shared with intervention group participants only Main intervention strategy and intensity not coded as outcomes not reported
Outcomes	Smoking cessation (biochemically validated) was collected but actual figures not reported so unable to include results in this meta-analysis. Peak flow values reported
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	States ‘women were randomised into two groups’.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Data not reported.
Selective reporting (reporting bias)	High risk	Actual figures not reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation of smoking status using urine cotinine and CO (cut-off levels not reported)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel unlikely to be blinded to educational intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Unclear risk	Not reported.
Equal baseline characteristics in study arms	Low risk	Groups similar with maternal age, fagerstrom scores, initial peak flow values and initial urine cotinine levels
Contamination of control group	Unclear risk	Not stated who delivered intervention.