Methods	Randomised controlled trial (SCRIPT trial II) of a cognitive behaviour therapy intervention to support women to stop smoking in pregnancy Study conducted in 4 public maternity clinics of the Jefferson County Health Department in Birmingham, Alabama (USA), with recruitment from September 1987 to November 1989
Participants	Inclusion criteria: Pregnant women who self-reported smoking during the first prenatal visit ‘at least one puff of one cigarette in the last 7 days’ Exclusion criteria: >= 32 weeks’ gestation, did not stay for visit or did not return, prisoners, or had difficulty reading the baseline questionnaire Recruitment: 1171/4352 (27%) of women screened at first prenatal visit were current smokers and 210 (3%) spontaneous quitters (who were included in a separate trial: Lowe 1997). 994/1061 (94%) eligible women agreed to participate and were randomised (C = 501, I = 493) Baseline characteristics: Mean cotinine 114 ng/mL. 45% had low cotinine levels (< 99 ng/mL) Mean age = 24.6 years; Mean education = 12.4 years; Black = 52% Progress+ coding: Low SES in this review as attending public maternity clinic
Interventions	Control: 2-minute talk on smoking in 30 minute group session at first antenatal visit in which women were urged to quit and given 2 pamphlets: “Smoking and the two of you”’+ “Where to find help if you want to stop” including the name, contact phone number and cost of their local program. Intervention: Based on cognitive behaviour therapy: (i) 15-minute standardised cessation skills and risk counselling session from trained female health education counsellor + 7-day self-directed cessation guide on how to quit written at 6th Grade level (ii) Clinic reinforcement (chart sticker) + letter from Doctor within 7 days (iii) Social support in form of a ‘buddy’ letter, contract and buddy tip sheet + monthly newsletter with testimonials, cessation tips and additional information on risks Main intervention strategy: Counselling (multiple intervention) compared to a less intensive intervention Intensity: Frequency (C = 1, I = 4), Duration: (C = 1, I = 3). Intervention provided by dedicated project staff: Efficacy study
Outcomes	Biochemically validated point prevalence abstinence at 4-8 weeks after first visit (midpoint), 32 weeks’ gestation (late pregnancy*). “Significant” reduction* if cotinine at least 50% value of baseline cotinine* Cost estimates. Separate trial reports data on spontaneous quitters (Lowe 1997).
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Attrition 180/994 (18%) due withdrawal from the service, miscarriage or abortion (C = 87, I = 93) were not included in analysis, leaving C = 414, I = 400 Further 15% lost to follow-up survey or cotinine analysis included as continuing smokers in this review
Selective reporting (reporting bias)	Unclear risk	Data on gestation and birthweight were collected but the published analysis is by stopping smoking and the timing of cessation rather than by allocation, so not included in outcome tables
Other bias	Unclear risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation of smoking status using salivary cotinine (cut-off >= 30 ng/mL)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Notes flagged. Educational intervention.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Low risk	Process evaluation showed 100% implementation of counselling and social support, and 88% for re-inforecement at subsequent visits
Equal baseline characteristics in study arms	Low risk	NS difference in baseline cotinine.
Contamination of control group	Low risk	Trained counsellor, not pregnancy care provider, delivered the intervention