Methods	Quasi-randomised trial of a self-help manual to support women to stop smoking in pregnancy Study conducted in public health maternity clinics in Gothenburg, Sweden, with data collection from 1987 to 1988
Participants	Inclusion criteria: Pregnant women registered as daily smokers (at least 1 cigarette per day), gestational age less than 12 weeks, and speak Swedish Exclusion criteria: Not further specified. Recruitment: 13/14 public health clinics participated. Women born days 1-10 of each month were allocated to the control group and women born on days 11-31 were allocated to the intervention group. Unequal group sizes were allocated as it was expected more intervention women would refuse to participate. 723 eligible continuing smokers were randomised (C = 231, I = 492). 417/492 (85%) of the intervention group agreed to participate, and the control group were not asked for consent Baseline characteristics: Mean cigs/day 16.8. Mean age 28.4 years. Progress+ coding: None.
Interventions	Control: Given an information sheet by their doctor with basic facts about smoking and pregnancy, as included in the last pages of the self-help manual Intervention: Given a self-help manual on stopping smoking, based on Windsor 1985. The manual was revised and pilot tested. The manual contained 2 phases, a preparatory (one week) and cessation phase. The smoker was given new assignments every day to the quit day and the tasks were based on the principle of behaviour therapy. The cessation period was followed for the first 5 days with new information daily Main intervention strategy: Health education (single intervention) compared to less intensive intervention Intensity: Frequency (C = 1, I=1), Duration (C = 1, I = 1). Intervention provided by existing staff (obstetrician provided self-help manual): Effectiveness study
Outcomes	Biochemically validated smoking cessation at 30-34 weeks’ gestation (late pregnancy*), 8 weeks postpartum (0-5 months), mean birthweight*, preterm births* (< 36 wks), low birthweight babies*, mean cigarettes per day at 30-34 weeks’ gestation among baseline smokers*. Mean cigarettes per day at baseline, week 12-14, week 30-34 among all randomised women, 8 weeks after delivery among baseline smokers and all randomised women
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)	High risk	Allocation by birth date is not random sequence. However, this study was included as interference is unlikely with birth dates
Allocation concealment (selection bias)	High risk	Allocation would not be concealed as allocated by birth dates (days 1-10 = control, days 11-31 = intervention)
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Loss to follow-up from miscarriage and moving out of district (C = 10% or 23, I = 11% or 46), not included in analysis. However, all other dropouts included as continuing smokers
Selective reporting (reporting bias)	Low risk	All primary outcomes appear to be reported.
Other bias	High risk	Unclear why there are 444 in intervention group and 209 in control group, when report states 10% of 231 were excluded and 11% of 492 were excluded
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation of smoking status using serum thiocynate (100 ng/mL)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel unlikely to be blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Unclear risk	Manual given to all women who agreed to participate (85% of total assigned to intervention - i.e. 15% refused to participate)
Equal baseline characteristics in study arms	Unclear risk	Only age and mean no of cigarettes reported.
Contamination of control group	Low risk	Unlikely control group would accidentally be given the self-help manual