Methods	Randomised controlled trial of midwifery counselling to support women to stop smoking in pregnancy Study conducted in a large UK maternity service. Data collection dates not specified
Participants	Inclusion criteria: Pregnant and booked for maternity care; <18 weeks’ gestation; currently smoking 1 or more cigarettes/day Practising midwives regularly attending antenatal clinic. 13 midwives selected for the intervention group and 13 for the control group Exclusion criteria: Not specified. Recruitment: All women identified as smokers in a busy teaching hospital with 3700 deliveries a year received a letter asking if they would like to participate. 100 women participated (described as ‘all 100 women contacted’) and were randomised (C = 50, I = 50) Baseline characteristics: ‘Contemplators’ (C = 70%, I = 60%), ‘pre-contemplators’ (C = 15%, I = 22%), ‘ready for action’ (C = 15%, I = 18%) No other baseline characteristics reported. Progress+ coding: None.
Interventions	Control: Usual care. Intervention: Midwives were trained to assess the stages of change and provide a behavioural intervention, using the Health Education Authority material “Helping pregnant smokers quit: training for health professionals”, 1994 Main intervention strategy: Counselling (single intervention) compared to usual care. Intensity: Frequency (C = 0, I = 5), duration (C = 0, I = 2)-based on estimated brief contact (< 5min) at a standard number of antenatal visits (8), as very little information about intervention provided. Usual care intensity: F = 0, I = 0 Intervention provided by existing staff: effectiveness study
Outcomes	Self-reported smoking cessation at 37 weeks (late pregnancy)*; and at 4 weeks (0-5 months*) postpartum Reduction in cigarettes/day; “stage of change” at 11 to 18 weeks vs 37 weeks. No biochemical validation of smoking status. Care providers’ views discussed
Notes	No process evaluation reported. Abstract data used. States ‘after one year’ which is assumed to be of year of the study, at 37 weeks’ gestation, as reported in figure one. As there were no quitters in the control group, the relapse rates of 4% within 1 month postpartum are assumed to be from the treatment group only
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated.
Allocation concealment (selection bias)	Unclear risk	Described as ‘randomly allocated’.
Incomplete outcome data (attrition bias) All outcomes	Low risk	94 of 100 randomised women followed up (reasons for attrition not reported). No ITT analysis reported. However, all drop-outs re-included as continuing smokers in this review
Selective reporting (reporting bias)	Unclear risk	All outcomes reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	High risk	No biochemical validation of reported smoking status.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel unlikely to be blinded to educational intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Unclear risk	Not reported.
Equal baseline characteristics in study arms	Unclear risk	Not reported.
Contamination of control group	Low risk	Midwives randomised so low risk of contamination.