Ratner 2001.

Methods	Country: Canada Setting: community Type: RCT
Participants	251 mothers who had quit smoking during pregnancy
Interventions	Intervention: Mothers received nurse‐delivered telephone support, relapse prevention training, and information resources. Control: usual care
Outcomes	Self‐report of smoking status Biological verification with exhaled CO
Type of intervention	Well‐child (peripartum)
Notes	Retention: 238/251 (95%)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Identification numbers randomly assigned to 2 groups, in blocks of 50, via a computer software package."
Allocation concealment (selection bias)	Unclear risk	No details provided
Incomplete outcome data (attrition bias) All outcomes	Low risk	Similar rates of follow‐up in both groups at 12 months and 95% retention (238/251)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation used at in‐person follow‐ups (89% of participants) "Only 1.4% of the self‐reports of abstinence were contradicted by CO readings of ≥ 10 ppm; these women were classified as smokers."