Methods	A randomised controlled trial of counselling intervention to support women to stop smoking in pregnancy The study was conducted in an antenatal clinic in Newcastle Hospital (UK), from March to May 1982
Participants	Inclusion criteria: All pregnant women currently smoking >= 1 cigarette a day at the time of the first antenatal clinic under care of 4 consultant obstetricians Exclusion criteria: Women 28 weeks’ gestation or more. Recruitment: 156 smokers identified in clinics and 5 were excluded as over 28 weeks’ gestation. 151 randomised (C = 74, I = 77) Baseline characteristics: Mean cigarettes per day before pregnancy: C = 18.3, I = 18. 1. Mean cigs per day at booking: C = 14.4, I = 15.1. Mean age: C = 25 years, I = 22.7 years. Partner unemployment: C = 53%, I = 57% Progress + coding: Low SES as study in ‘deprived area’ and high partner unemployment
Interventions	Control: Usual antenatal care with possible exposure to a concurrent television series (6 × 10-minute programme on stopping smoking in pregnancy). Intervention: (i) 10 minutes anti-smoking advice from SHO (Resident) based on Health Education Council Booklet “So you want to stop smoking for you and your baby”, an additional leaflet from the same source, and copies of the booklet for other family members; (ii) woman’s GP sent a letter describing the purpose of the study and a booklet, asked to reinforce the information at usual contacts; (iii) 2 weeks later a letter of reinforcement was sent to the woman; (iv) four weeks later there was a pre-planned home visit to provide anti-smoking advice with a letter of the same advice sent if the woman was not at home; (v) possible exposure to the concurrent TV series. Main intervention strategy: Health education (multiple intervention) compared to usual care Intensity: Frequency: (C = 0, I = 4), Duration (C = 0, I = 2) Estimate. Usual care intensity: F = 1. D = 1 Intervention provided by existing staff (resident): Effectiveness study
Outcomes	Self-reported smoking cessation 9-16 weeks after booking visit (late pregnancy*). Mean cigarettes per day* (the SD used in the analysis in this review was calculated from a P value of 0.05 given in the paper)
Notes	Short interval between intervention and assessment.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as balanced “simple random allocation” in blocks.
Allocation concealment (selection bias)	Unclear risk	Information not provided.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Small loss to follow-up, some missing data but balanced across groups. Attrition 6/151 (4%, C = 3, I = 3): not pregnant (C = 1), 1 guilt over previous stillbirth (I = 1), and miscarriages or medical complications (C = 2, I = 2). 145 included in analysis (C = 73, I = 72)
Selective reporting (reporting bias)	Low risk	None apparent.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	High risk	No biochemical validation of self-reported smoking cessation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Neither women nor providers blinded to this educational intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	High risk	A home visit at 4 weeks was made to the remaining 76 test patients. 31 (41%) were found at home; 29 were given further antismoking advice; 45 (59%) were out and a letter of encouragement was left
Equal baseline characteristics in study arms	Unclear risk	Mean age of test mothers 22.7, controls 25. Report notes other variables were equal, but figures are not reported
Contamination of control group	Low risk	Main component home visit.