Johnson 2000.

Methods	RCT, 2 arms with individual randomisation.
Participants	Setting: 254 women in 5 hospitals in Canada (unclear).  Inclusion criteria: reported as ‘Women who gave birth at one of 5 hospitals who: identified herself as a smoker before pregnancy; quit smoking once aware of pregnancy or in attempting to become pregnant; ceased smoking for at least 6 weeks before delivery; if smoking occurred in 6 week period immediately before delivery smoked on fewer than 6 occasions; gave birth to a healthy infant not requiring hospitalisation beyond discharge of the mother; planned to remain in hospital for at least 24 hours; able to read and comprehend English; could be contacted by telephone’.
Interventions	Intervention group: 125 women in treatment group included in analysis. Postpartum counselling intervention to prevent smoking relapse. The intervention was provided one‐to‐one by specially recruited and trained nurses. Women received initial counselling in hospital along with pamphlets and no smoking signs for their homes. There were then 8 postnatal phone calls (weekly during the first month, then fortnightly) which lasted between 1 and 20 minutes. Only 25% of the intervention group received all 8 calls. Control group: 126 women in the analysis. Received usual care (did not include any information about effects of smoking or prevention of smoking relapse).
Outcomes	Self‐report smoking status, Bedfont EC50 Smokerlyzers, Carbon monoxide (CO) readings of 10 or more parts per million (ppm).  Continuous abstinence: complete avoidance of smoking during the entire 6‐month period. Smoking cessation self‐efficacy was measured by the Smoking Abstinence Self Efficacy Scale.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomisation (in groups of 50) randomisation via ‘computer software package’.
Allocation concealment (selection bias)	Unclear risk	Unclear  “identification numbers randomly assigned to two groups”.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not described.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	At 6 months after delivery both groups were interviewed by research assistants in own home who had not delivered the intervention and who were reported to be blind to group assignment.   Carbon monoxide in expired air was also measured for some women.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Follow‐up interviews actually occurred between 24 and 50 weeks after baseline data collection. 11 interviews conducted away from woman’s home and 19 were over telephone (so breathalyzer not completed. 6 from control and 4 from treatment refused to participate. They (the 10) were coded as failing to maintain abstinence as daily smokers – self‐efficacy scores were not imputed for these 10 women. 3 women excluded from analysis: reported as: ‘ 1 assigned to control group but inadvertently given intervention and 3 were assigned to treatment group but did not receive any telephone contacts’.
Selective reporting (reporting bias)	Unclear risk	Assessment from published study report.
Other bias	Unclear risk	It was reported that smoking related variables were similar in the 2 groups at baseline.