Secker‐Walker 1998.

Methods	Randomised controlled trial of a counselling intervention to support women to stop smoking in pregnancy and prevent relapse postpartum. The study was conducted in offices of the 'University Associates in Obstetrics and Gynecology' in Vermont (USA), with recruitment from October 1988 to October 1992.
Participants	Inclusion criteria: Woman who reported smoking 1 or more cigarettes per day at onset of pregnancy. Exclusion criteria: Not further specified. Recruitment: Women recruited through the state‐supported (Maternal and Infant Care) prenatal clinic for underserved women or attending the Adolescent clinic for women 12 to 18 years. 524/544 (96%) women who were invited agreed to participate and were randomised. 399 current smokers (C = 202, I = 197); 125 spontaneous quitters (C = 63, I = 62) (separate paper). Baseline characteristics: Smokers: Mean cigarettes per day before pregnancy C = 25.1, I = 26.1; mean cigarettes per day at first prenatal visit: C = 11.8, I = 13.4. Another smoker in the household (C = 82.6%, I = 78.5%). Mean age: 23 years, < high school (C = 41%, I = 48%), 27% married; Medicaid recipients (C = 73.1%, I = 71.9%); Adolescent clinic (C = 13.5%, I = 11.9%). Spontaneous quitters: Mean cigarettes per day before pregnancy (C = 14.1, I = 13.5). Other smokers in household (C = 64%, I = 70%). Mean age: C = 21.9, I = 20.9; < high school (C = 27%, I = 36%); 29% married; Medicaid recipients (C = 68.1%, I = 65.1%); adolescent clinic (C = 14.9%, I = 11.4%). Progress + coding: Low SES.
Interventions	Control: Physician acknowledged women's smoking, gave a rationale for quitting, strong recommendation to quit and provided smoking cessation booklet designed for pregnant women. All participants received: baseline questionnaire, measurement of exhaled CO, and brief standardised health risk message from a research nurse about the effects of smoking on the fetus and pregnancy. Intervention: A structured smoking cessation protocol provided by physicians trained in its use (Secker‐Walker 1992) at 1st, 2nd, 3rd and 5th visits: acknowledging the woman’s smoking, her exhaled CO level, any progress towards quitting, rationale for and unambiguous recommendation to quit, asking how she felt about quitting and acknowledging her response, asking how she could be helped and telling her about the counsellor, eliciting a commitment to change smoking behaviour before the next prenatal visit and referring her to the counsellor. The aim was to gain her agreement to set a quit date, a date when she would quit for 24 hours or a date when she would cut her consumption by half. Counsellor advised women on ways to accomplish the behaviour change. 2nd, 3rd, 5th and 7th visit included praise for those who had quit with referral to counsellor for help in staying quit. 36 week visits included a briefer protocol followed with referral for those who wanted to change, praise for success and referral to a nurse counsellor if smoking. Main intervention strategy: Counselling (multiple intervention) compared to less intensive intervention. Intensity: Frequency (C = 1, I = 5), Duration (C = 1, I = 3). Intervention provided by existing staff, with referral to a counsellor: Effectiveness study.
Outcomes	Biochemically validated 7‐day point prevalence abstinence at 36 weeks' gestation (late pregnancy *) and 1 year postpartum*. Mean cigarettes per day at 36 weeks' gestation* and 12 months postpartum. Mean exhaled CO*. Mean birthweight*. LBW*. Relapse prevention at 36 weeks' gestation (late pregnancy*) and 12 months postpartum reported in associated reference (Secker‐Walker 1998b) Preterm births* are reported in attrition and are re‐included in both numerator and denominator for this outcome.
Notes	Methods included a detailed process evaluation of participants' views and recall of provider advice. Sample size justification. Separate paper reports relationship between exhaled CO and birthweight (Secker‐Walker 1997b)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as "randomly assigned".
Allocation concealment (selection bias)	Unclear risk	No details provided.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	High attrition. More than 25% lost to follow‐up in pregnancy and more than 30% lost to longer‐term follow‐up. Smokers: 109/399 (27% attrition) 24 (6%) women with miscarriage (14), fetal demise (5) and infant deaths (5) were excluded from analysis and are not reported by group allocation. Report states 376 women remain included (instead of 375) (C = 191, I = 185). 68 women transferred care (C = 34, I = 34), 17 delivered before 36 weeks (C = 8, I = 9) and were not included in 36‐week analysis. 12 women withdrew from study (C = 5, I = 7) and 3 lost to follow‐up (C = 3), and were re‐included as continuing smokers in this review, but are not included in mean cigarettes per day or perinatal outcomes. 114 (I) and 110 (UC) were contacted 1 year after birth, including 16 (I) and 18 (UC) lost to follow‐up during pregnancy. Women with adverse outcomes were not included in the analysis. Spontaneous quitters: 33/125 (26%) attrition. Women with miscarriage (5), abortion (1), infant death (1), pregnancy loss (1), moving to another clinic or moving (22; C = 13, I = 9), delivering before 36 weeks (I = 2). All excluded from analysis leaving C = 48, I = 44.
Selective reporting (reporting bias)	Unclear risk	Only smoking outcomes reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Self‐reported cessation with biochemical validation by exhaled CO (< 6 ppm) or urinary cotinine (< 500 ng/mL).
Blinding of participants and personnel (performance bias) All outcomes	High risk	Intervention by clinic staff. Notes flagged.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	Low risk	Methods included a detailed process evaluation of participants' views and recall of provider advice and suggests ‘to a large extent the intervention was implemented as planned’.
Equal baseline characteristics in study arms	Unclear risk	No significant differences except for larger proportion of women in intervention group had not made a quit attempt in the past.
Contamination of control group	Unclear risk	No women in cessation group received cessation counselling beyond the physician advice. Though the same physician provided advice so unclear if this was influenced by the intervention.