McBride 1999b.

Methods	Setting: 2 Health Maintenance Organisations, USA Recruitment: Pregnant women who had booked a prenatal appointment, by mail
Participants	897 pregnant smokers and recent quitters (44% already quit) not selected for motivation to quit; av. age 28, av. cigs/day 15 before pregnancy, 5 if still smoking
Interventions	1. S‐H booklet only 2. Prepartum intervention: 3 proactive TC calls av 8½ mins, approx 2 weeks after S‐H mailing, and 1 m and 2 m later. Tailored letter, S‐H book. After 28‐week follow‐up sent relapse prevention kit 3. Pre‐ and postpartum intervention: as 2, plus 3 calls within first 4 m postpartum, av 7.7 mins. 3 newsletters
Outcomes	Abstinence at 12 m postpartum (7‐day PP) Validation: Saliva cotinine requested by mail, < 20 ng/mL. Self‐reported rates used in analyses, no difference in confirmation rates between groups
Notes	Arms 3+2 vs 1, effect of TC versus S‐H only
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised, method not described
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation used, not reported: Quote: "since there were no between‐group differences in the proportion of saliva samples returned or the proportion confirmed, the primary trial outcomes were based on self‐reported smoking status."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up 13% at 12 m, not different by group, losses included as smokers