Methods	Randomised controlled trial of self-help booklets to support women to stop smoking in pregnancy Study conducted in 5 health centres of the same HMO in Los Angeles (USA), from 1985 to 87
Participants	Inclusion criteria: English-speaking women attending 1 of 5 health centres for prenatal care, < 18 weeks’ gestation; still smoking >= 7 cigarettes a week Exclusion criteria: Not specified further. Recruitment: 323 who self-reported still smoking >= 7 cigs/week were randomised (C = 158, I = 165). 242 included in final analysis (C = 116, I = 126). 228 women who had spontaneously quit also included (C = 108, I = 110) Baseline characteristics (smokers): Prepregnancy smoking: 27.3% 1-10 cigs/day, 14% 11-19 cigs/day, 58.7% 20+ cigs/day. At intake: 71.9% 1-10 cigs/day, 14.9% 11-19 cigs/day, 13.2%20+ cigs/day. Spontaneous quitters: mean pre-pregnancy cigarettes/day = 10.3 Smokers: 64% white, 73% had high school or some college education, 59.9% married Progress+ coding: None.
Interventions	Control: 2-page pamphlet on hazards of smoking and on the need to quit; 2 minutes discussion with a health educator (within a 45 minutes individual conference); advised of free 5 session smoking cessation program available through the HMO. Coverage in antenatal classes remained unchanged. Intervention: As for the control group + first of series of 8 self-help booklets aimed to increase motivation for quitting; teach behavioural strategies for cessation and relapse prevention; 3 minutes introduction to these by health educator; asked to make a commitment to read the first 1 and list reasons for not smoking; others mailed weekly. Booklets were pregnancy-specific, multi-ethnic, and at a 9th Grade reading level Main intervention strategy: Counselling (single intervention) compared to less intensive intervention Intensity: Frequency (C = 6, I=6), Duration (C = 4, I = 4). Estimate based on uptake of optional HMO sessions × 5 approximately 20-40 mins Intervention provided by existing health staff: effectiveness study
Outcomes	Biochemically validated abstinence at 34 weeks’ gestation (late pregnancy*) Ershoff 1995 reports relapse prevention* among women who had spontaneously quit Ershoff 1990 reports birth outcomes (mean birthweight*; low birthweight*; preterm birth* (< 37 weeks); stillbirths*) and cost outcomes (economic evaluation) Associated reference (Mullen 1991) describes question structure’s to improve accurate disclosure of smoking status
Notes	SDs for mean birthweight were not reported, therefore we calculated a mean SD from 13 studies with available birthweight SDs (578) to include in this review, as recommended by the cochrane handbook
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information
Allocation concealment (selection bias)	High risk	The authors state that women had been randomised in advance of their visit. It was not clear how women were recruited to the study or gave consent for participation.The health educator turned over a ‘pre-assigned card’ to randomise women
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Smokers: Attrition I = 39/165, C = 44/158 not included in analysis. Losses due to termination (C = 11, I = 7); miscarriage (C = 13, I = 12); disenrolment or transfer to another HMO (C = 18, I = 20) Spontaneous quitters: Attrition 22% - Abortion (n = 5), miscarriage (n = 17), disenrolment from HMO or transfer (n = 25) Not re-included in analysis for this review as excluded for medical reasons or moving
Selective reporting (reporting bias)	Unclear risk	None apparent.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation by urinary cotinine levels. For participants reporting no smoking and low exposure to passive smoke urine cotinine had to be less than or equal to 10 ng/mL. For participants reporting a relapse and high exposure to passive smoke some values could be as high as 29 ng/mL though at least 1 sample had to be 10 ng/mL or less
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	The authors state that the health educator delivering the intervention was not aware of group allocation, but materials were provided to the experimental group at the clinic visit. Prenatal care providers were blinded to group assignment and no effort was made to modify their usual counselling practices
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Low risk	Process evaluation reports good implementation.
Equal baseline characteristics in study arms	Unclear risk	With the exception of partners smoking status.
Contamination of control group	Unclear risk	Prenatal care providers no involved in intervention so risk of contamination likely to be low