Methods	Quasi-randomised trial of counselling and optional nicotine replacement therapy, to support women to stop smoking in pregnancy Study conducted in a large midwifery centre in the Netherlands, with data collection from 1996 to 1998
Participants	Inclusion criteria: All pregnant women attending first prenatal visit. Exclusion criteria: Inability to speak Danish, age below 18 years, gestation of more than 22 weeks, verified psychiatric diseases, and alcohol or drug abuse Recruitment: 696/905 (77%) eligible women attending first antenatal clinic who smoked agreed to participate in study (informed consent) and were randomised (C = 347, I = 348). 647 included in final analysis (C = 320, I = 327) Baseline characteristics: Mean cigs/day = 11, Significant difference in partner smoking (I = 67%, C = 77%, P = 0.03), mean salivary cotinine (C = 141, I = 139) Mean age 29 yrs, > 12 yrs in school (C = 45%, I = 43%), mostly married Progress+ coding: None.
Interventions	Control: Usual care, which included routine information about the risk of smoking in pregnancy and general advice on smoking cessation or reduction in a standard 30-minute consultation Intervention: (i) Extended initial consultation (from 30 to 40 minutes) which included a dialogue about smoking and motivation for cessation (ii) written information about risks of smoking and passive smoking (iii) invitation to join smoking cessation program, based on CBT. The program involved 9 appointments (individually or in a group) over a period of 14 weeks. 3 attendances prepared participants for quitting and 6 were used to maintain cessation and to hand out NRT. CO readings at each visit (iv) NRT offered to all women (2 mg gum or 15 mg patch × 16 h) for 11 weeks (v) encouragement at subsequent 5-6 antenatal visits. Main intervention strategy: Counselling (tailored) compared with usual care. Intensity: Frequency (C = 0, I = 6), Duration (C = 0, I = 6). Usual care intensity: F = 1, D = 1 Intervention provided by specially trained midwife (study staff): Efficacy study
Outcomes	Biochemically validated smoking cessation at 37 weeks’ gestation (late pregnancy*), mean birthweight*, low birthweight*. Preterm births* reported in attrition and re-included in both numerator and denominator for this outcome Regression analysis for passive smoke exposure, years of education reported
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	Quasi-randomised by odd or even birth date. Included in review despite inadequate sequence generation as there is a low likelihood of interference with birthdate allocation
Allocation concealment (selection bias)	High risk	Quasi-randomised by odd or even birth date.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Attrition: 10 had miscarriage or stillbirth (C = 5, I = 5); 21 moved out of area (C = 12, I = 9); 17 had a premature delivery (C = 10, I = 7). These were excluded from analysis
Selective reporting (reporting bias)	Low risk	Primary outcomes appear to be reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Smoking cessation validated by salivary cotinine <= 30 ng/mL
Blinding of participants and personnel (performance bias) All outcomes	High risk	Providers and participants not able to be blinded to educational intervention and NRT provision not blinded (no placebo)
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated.
Incomplete implementation	High risk	Only 87 women (27%) accepted participation: 81 in a group and 6 women accepted an individual smoking cessation program. 71 of 87 participants (82%) participated in 3 or more of a total of 9 meetings in the smoking cessation program. 75 (86%) of 87 women participating in the smoking cessation program were using nicotine substitution in the form of a 15 mg nicotine patch (16 h/day) or 2 mg nicotine chewing gum or a 15 mg nicotine patch (16 h/day) plus 2 mg nicotine chewing gum
Equal baseline characteristics in study arms	Unclear risk	Mostly equal except more women were exposed to passive smoking in the home in the intervention group (77%) than in the control group (67%) (P = 0.03)
Contamination of control group	Unclear risk	The strengths of the study include absence of treatment diffusion as all participants in the intervention group were seen by specially trained midwives as opposed to participants in the control group who were all consulting midwives without such training. The study enjoys a second advantage which is that intervention and control group participants were seen at different week days and hence could not easily share information. The secretaries summoning the pregnant women were continuously reminded about this allocation criterion to avoid treatment diffusion between the intervention and the control group. p814