Methods	3-armed randomised controlled trial of self-help materials and counselling to support women to stop smoking and prevent relapse during pregnancy and postpartum Study conducted at a large Boston HMO (USA), with recruitment from March 1986 to September 1988
Participants	Inclusion criteria: English-speaking literate women enrolling in prenatal care; who reported themselves as currently occasional or regular smokers or who had quit smoking in the previous 3 months Exclusion criteria: < 18 years of age; > 24 weeks’ gestation. Recruitment: 1442 women screened during early pregnancy class. 317 current smokers and recent quitters were identified. Participants from 3 centres were randomised to control and first intervention (I1) arms, and participants from a fourth arm were not randomly allocated and are not included in analysis ion this review. 93/317 attrition, leaving 224 included (C = 78, I1 = 71, I2 (not randomised) = 75). Baseline characteristics: Baseline smokers : 142 (C = 47, I1 = 43, I2 = 52) and baseline spontaneous quitters: 104 (C = 36, I1 = 34, I2 = 34) analysed at 6 months gestation. Majority 17-28 years, No participants less than high school, less than $US 20000/yr (C = 18.7%, I1 = 20%, I2 = 32.3%). Over 80% married and majority white. Progress+ coding: None.
Interventions	Control: Routine obstetric care, including a mailed list of community-based smoking cessation resources other pregnancy-related health education materials. Brief repeated counselling by obstetricians and midwives for both groups as part of routine care. Intervention 1: Pregnancy-specific self-help manual (Am Lung Assoc and Harvard Community Health Plan (HMO)) and audiotape on safe aerobic exercise and pregnancy-related relaxation, mailed with other health-related education. Smoking component emphasised behavioural strategies for quitting, issues and concerns specific to pregnant women, non-smoking as part of a continuum of care in pregnancy; included a maintenance section for the postpartum period Intervention 2: As for I1 plus training for obstetrician and nurse practitioner to provide training, and support letters from physician Main intervention strategy: Health education (single intervention) compared to usual care. Intervention 1 and control compared in this review as the I2 group was not randomised. Intensity: Frequency (C = 0, I = 2), Duration (C = 0, I = 1). Usual care intensity: F = 3, D=2 Intervention provided by dedicated project staff: Efficacy study
Outcomes	Smoking cessation for smokers and spontaneous quitters at 6 months gestation (late pregnancy* and 8 weeks postpartum (0-5 months*) Description of costs.
Notes	Substantial misclassification of non-smoking self-report at 6 months gestation 24% controls 21% intervention (and 30% in clinic where the intervention was more intensive)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Table of random numbers. Allocation to intervention arm 2 was not randomised but offered to all eligible enrollees at 1 clinic: therefore data from this intervention arm are not included in the review
Allocation concealment (selection bias)	Unclear risk	No information provided.
Incomplete outcome data (attrition bias) All outcomes	High risk	93/317 (29%) were excluded from analyses due to miscarriage, therapeutic abortion, moving, or left the Harvard Health Plan, leaving 217 included. However, 246 (C = 83, I1 = 77, I2 = 86) ‘baseline smokers and spontaneous quitters’ included in analysis at 6 months gestation and 219 included in 8 weeks postpartum. It is not clear which randomised women are included in analysis
Selective reporting (reporting bias)	Unclear risk	None apparent but results were not simple to interpret.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation in 50% women. Those refusing urine test were coded as smoking
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	State that caregivers were blind as materials to the intervention group were mailed. Not feasible to blind women
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Low risk	All women received materials for intervention 1 used in this review. Some implementation problems noted with the counselling arm (I2), but that was not included in this review.
Equal baseline characteristics in study arms	High risk	Differences in educational attainment.
Contamination of control group	Low risk	Unlikely with mail out of materials.