Methods	Randomised controlled trial of counselling to support women to stop smoking during pregnancy in the USA. Location and dates of data collection not reported (abstract only available)
Participants	Inclusion criteria: Self-reported smokers presenting for prenatal care before 24 weeks’ gestation Exclusion criteria: Not specified. 150 women randomised. Data for only 43 women (C = 20, I = 23) who had delivered by the time of report are available. 2 women in control group had baseline cotinine levels consistent with abstinence so are not included (C = 18, I = 23) Baseline characteristics: Not reported. Progress+ coding: None.
Interventions	Control: Discussion of smoking risks by a nutritionist and again by a resident physician at initial prenatal visit Intervention: Control + regular meetings with a smoking cessation counsellor and physician reinforcement at each visit. The women also received biochemical feedback from urine cotinine Main intervention strategy: Counselling (multiple intervention) compared to a less intensive intervention Intensity: Frequency (C=1, I=5); Duration (C=1, I=3). Estimates for intervention as little detail provided
Outcomes	Biochemically validated point prevalence abstinence at term or birth (late pregnancy*); >50% reduction in mean cotinine*; and mean birthweight*
Notes	SDs for mean birthweight were not reported, therefore we calculated a mean SD from 13 studies with available birthweight SDs (578) 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)	Unclear risk	Not reported.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	One woman in the intervention group dropped out of the study and was not included in the original analysis but has been re-included as a continuing smoker in this review, but not included in the mean birthweight analysis
Selective reporting (reporting bias)	High risk	Preliminary results only available. Final results not reported and unable to be accessed
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation by urine cotinine but cut-off levels not reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not feasible for participants and personnel to be blinded to counselling 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	Unclear risk	Baseline characteristics not reported (abstract only).
Contamination of control group	High risk	Appears that same physician provided advice to control and intervention women, and not clear if this was not repeated for control group