Methods	Cluster-randomised controlled trial of brief GP counselling to support women to stop smoking in pregnancy and prevent relapse postpartum Study conducted in Western Norway from November 1986 to November 1987
Participants	Inclusion criteria: No indications of serious social or medical problems, living with a partner, and smoking at least 5 cigarettes per day before pregnancy and still smoking at least 1 cigarette per day at the first checkup Exclusion criteria: Not further specified. Recruitment: All 398 GPs in western Norway were invited by mail to participate in the study. 187 participating GPs were asked to recruit 4 pregnant and 4 non-pregnant women for the study, at the first checkup in the first trimester. 1/3 pregnant and non-pregnant women ended up in control groups. The GPs who recruited pregnant women for the intervention groups recruited non-pregnant women for the control groups. 2379 pregnant women screened, 674 fulfilled inclusion criteria, 144 refused to participate (21%). 530 pregnant women were randomised (unclear how many each group) Baseline characteristics: Mean age starting smoking 27.6, mean cigs per day = 9.5. Mean age 25.9. 18-34 years of age, all living with a partner Progress+ coding: None.
Interventions	Control: Ordinary control programme during pregnancy and for first year after delivery (usual care) Intervention: (i) < 15 mins GP consultation at initial visit about hazards of smoking, how to stop and how to avoid relapse; (ii) information about problems related to ‘the smoking fetus’; (iii) delivered with aid of a 5-page ‘flip-over’; (iv) 8-page booklet. Women invited to consult their GPs after 1, 6, 12 and 18 months to discuss their smoking habits Main intervention strategy: Counselling (multiple intervention) compared with usual care Intensity: Frequency (C = 0, I = 3), Duration (C = 0, I = 1). Usual care intensity: F = 0, D = 0 Intervention provided by existing staff (GPs): Effectiveness study
Outcomes	Self-reported abstinence 6 months after study entry (late pregnancy*), biochemically validated at 12 months after study entry (0-5 months postpartum*), self-reported abstinence 15 (6-11 months postpartum*) and 18 months after study entry (12-17 months postpartum*) Sef-reported reduction and increase in smoking. An associated reference (Haug 1992) reports results of a survey of GPs delivering the intervention
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	GPs described as randomly allocated.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	High risk	180/530 dropped out due to spontaneous abortions (24), serious complications (8), moved to another district (31) or for other unknown reasons (117). Only 350/530 (C = 98, I = 252) included in analysis and we were unable to re-include those lost to follow-up for other reasons in this review as they were not reported by group allocation. Further dropouts not explained (C = 97 and I = 244 in outcome tables-re-included in this review as continuing smokers)
Selective reporting (reporting bias)	High risk	Not clear if biochemically validated outcomes reported.
Other bias	High risk	Unequal recruitment to study arms (higher recruitment in intervention arms)
Biochemical validation of smoking abstinence (detection bias)	High risk	Biochemical validation of smoking only at study entry and after 12 months (urinary thiocynate). Unclear if those who had high thiocynate levels were considered smokers. No cut-off levels reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not feasible to blind participants and personnel to counselling intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	High risk	59% residents did not document consultation. 1 component dropped
Equal baseline characteristics in study arms	Unclear risk	Not reported.
Contamination of control group	High risk	Same providers asked to provide control and intervention arms for pregnant and non-pregnant women