Methods	Randomised controlled trial of counselling to support women to stop smoking in pregnancy and postpartum Study conducted at the University of Vermont, Burlington (USA), with recruitment from May 1984 to June 1987
Participants	Inclusion criteria: Pregnant women less than 25 weeks’ gestation, smoking at least 1 cigarette a day Exclusion criteria: Not further specified. Recruitment: Women receiving prenatal care from obstetricians and nurse-midwives, or residents through Maternal, Infant & Child clinic for under-insured or non-insured women, were randomly assigned (23% Medicaid in study). 775/808 (96%) smokers invited agreed to participate. 175/775 women spontaneously quit before their first visit and were randomised into a separate study of relapse prevention (C = 86, I = 89) (Secker-Walker 1995). 600 smokers randomised (C = 300, I = 300). Baseline characteristics: Mean cigarettes per day pre-pregnancy C = 25.1, I = 24.4. Mean cigarettes per day at first prenatal visit: C = 12.4, I = 14.1 Mean age: 24 years; Less than high school: C = 30.7%, I = 28.2%; Medicaid recipient C = 23.2%, I = 25.3% (50% private insurance) Progress+ coding: Low SES due to high rates of women who hadn’t completed high school
Interventions	Control: ‘Usual advice about smoking provided by obstetrician or midwife’. Intervention: Counselling from a trained health educator who: addressed concerns re smoking and pregnancy, health benefits of stopping, perception of the advantages and disadvantages of stopping, problem solving around those issues and coming to a decision. If agreeing to quit and formulating a plan, women were provided with skills rehearsal and a pregnancy-specific booklet. Follow-up at second antenatal clinic, 36 weeks and 6-week check (where infant health and parental role modelling was discussed) and re-encouraged to quit. Health educators given selected readings, discussion, rehearsal with psychologist + health educator (both former smokers) about smoking and smoking cessation counselling techniques + American Lung Association training group for class leaders + 4-week pilot The relapse prevention component was individualised but carried out within a defined protocol. Counselling about preventing relapse and a booklet. Follow-up at second antenatal clinic, 36 weeks and 6-week check (where infant health and parental role modelling was discussed) Main intervention strategy: Counselling (multiple intervention) compared to usual care Intensity: Frequency (C = 0, I = 3), Duration (C = 0, I = 3). Usual care intensity: F = 1, D = 1 Intervention provided by dedicated project staff: Efficacy study
Outcomes	Smoking cessation at 36 weeks’ gestation (75% biochemically validated with cotinine) (late pregnancy*), Long-term quitting measured at 8-15 months’ pp (6-11 months pp*) , 16-24 pp (18 months postpartum), and 25-54 pp (self-reported) Relapse prevention* reported in associated reference (Secker-Walker 1995). Mean birthweight*, low birthweight*, other smoking-related complications (PPROM, placental abruption and placenta praevia) Reduction in mean cotinine/creatinine ratio at 36 weeks’ gestation
Notes	Sample size calculated for 10% increase (from 10% to 20%) in quitting. No adjustment for misclassification. Recall of advice about smoking. Separate paper (Secker-Walker 1992) evaluates training program for residents.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as “randomly assigned”.
Allocation concealment (selection bias)	Unclear risk	Not stated. Unclear when randomisation took place.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Smokers: Attrition 39/600 (6.5%) due to miscarriage (27), fetal deaths (7), infant deaths (5), 48 transferred care (C = 24, I = 24), and were excluded from analysis, leaving C = 258, I = 255 Further losses were: 41 dropped out of study (C = 4, I = 37), and 59 were lost to follow-up (C = 28, I = 31), but were re-included in this review as continuing smokers, but are not included in mean birthweight and other birth outcomes analyses. Significant difference in pregnancy dropout rates for I (13% drop-out rate ) and C (1.4% drop-out rate). Those lost to followup smoked more Voluntary drop-outs treated as continuing smokers for some analyses Spontaneous quitters: attrition 8/175 (5%) due to miscarriage (5), abortion (1), fetal demise (1), and infant death (1) and lost records (2) were excluded from analysis, leaving C = 80, I = 85. Further attrition: transferred care (15)-not reported by study arm, dropped out of study (9), lost to follow- up (8), re-included in baseline as continuing smokers in this review Differential withdrawal in I and C groups a concern; good information collected on drop-outs being different
Selective reporting (reporting bias)	Unclear risk	Data collected not specified. Only smoking outcomes reported
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Urinary cotinine/creatinine ratio levels measured at 36 weeks (< 80 ng/mg)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Educational intervention in antenatal clinics.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Low risk	All but 9 intervention women not lost to follow-up received all 3 counselling sessions before 36 weeks, and 89% received the postpartum 1
Equal baseline characteristics in study arms	High risk	Mostly similar but women in intervention group tended to smoke more cigarettes at time of their first visit
Contamination of control group	Low risk	A separate health educator provided intervention.