Hovell 2009.

Methods	Country: USA Setting: at home RCT
Participants	Mothers who smoke, with children younger than 4 years
Interventions	Intervention: 10 in‐person at‐home and 4 telephone counselling sessions over 6 months, with additional pre‐quit and post‐quit telephone sessions Control: referral to the free California Smoker's Helpline (usual care)
Outcomes	Eighteen‐month follow‐up from baseline: • Children's urine cotinine concentration • Parents' smoking status ‐ self‐reported and confirmed with salivary cotinine • Air nicotine measured in randomly selected homes
Type of intervention	Child with health problems (ill‐child health care)
Notes	Recruited from the Supplemental Nutrition Programme for Women, Infants, and Children
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"random number list was used to assign pairs of participants matched on child's gender, ethnicity and recruitment site"
Allocation concealment (selection bias)	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	18‐Month interview 64/74 control group and 66/76 intervention group
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Data collection research assistants were blind to group assignment, and control families were unaware of counselling procedures. Investigators were blind to results until all data were collected."
Other bias	High risk	However, "baseline children's urinary cotinine concentration was significantly higher among controls, indicating that randomization did not balance the groups with respect to cotinine".