Methods	Randomised controlled trial of stage of change orientated motivational interviewing to support women to stop smoking in pregnancy The study was conducted in infertility and prenatal clinics in 3 hospitals in Ontario (Canada), with data collection from January 1996 to July 1999
Participants	Inclusion criteria: Newly referred infertile and pregnant patients who reported smoking more than 3 cigarettes in past 6 months Exclusion criteria: Women attending genetic counselling or with habitual abortion or who had previously been evaluated in consultation Recruitment: All women attending infertility and prenatal clinics who reported smoking were invited. Unclear how many were eligible. 110 pregnant women randomised (I = 56, C = 54) Baseline characteristics: Mean cigs/day = 12.19 (SD 6.81); (I = 13.43 +−7.07, C = 12 +− 6.69
Interventions	Control: Standard information that was already provided in the clinics about the impact of smoking on pregnancy Intervention: Scripted stage-based information and encouragement to quit at each prenatal visit by physicians, Stage-specific information booklet, optional referral for more in-depth counselling in a smoking cessation clinic Main intervention strategy: Counselling (tailored intervention) compared with usual care Intensity not coded as outcomes unable to be included in meta-analysis
Outcomes	Stage of change, biochemically validated cessation at 12 months post follow-up but data for intervention and control groups were combined so outcomes were unable to be included in this review. See Table 1 for description of outcomes. Relative value of intervention components reported.
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomised using computer-generated, blocked schedule, administered through numbered, opaque, sealed envelopes
Allocation concealment (selection bias)	Low risk	Opaque sealed envelopes.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No attrition reported and not stated how, if any, dropouts were assessed
Selective reporting (reporting bias)	High risk	Smoking cessation outcomes not reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Unclear risk	Biochemical validation with exhaled CO, but levels used to determine smoking status were not reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Providers and women not able to be blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated whether outcome assessors blinded.
Incomplete implementation	Unclear risk	Process evaluation not reported.
Equal baseline characteristics in study arms	Low risk	No significant differences noted.
Contamination of control group	High risk	Same care providers offering intervention and control interventions, therefore high risk of contamination