Methods	Randomised controlled trial of home-based counselling to support women to stop smoking in pregnancy Study conducted in 2 hospitals in Glasgow, Scotland (UK), with recruitment from March 2001 to May 2003
Participants	Inclusion criteria: Women reporting smoking at prenatal booking visit and less than or equal to 24 weeks’ gestation Exclusion criteria: Not further specified. Recruitment: 762/1684 (45%) eligible women agreed to participate (C = 411, I = 351) Baseline characteristics: Current mean cigarettes per day: C = 11.3, I = 11.7; At least 1 other smoker in house: C = 66%, I = 65% Mean age: C = 26.9, I = 26.5; Most deprived social category (6-7): C = 73%, I = 69% Progress+ coding: Low SES.
Interventions	Control: Midwives provided standard health promotion including information on smoking in pregnancy from a book given to all women in pregnancy in Scotland Intervention: Women also were offered 2-5 additional home visits of about 30 minutes duration from the same study midwife Main intervention strategy: Counselling (single intervention) compared to usual care. Intensity: Frequency: (C = 0, I = 4), Duration (C = 0, I = 4). Usual care intensity: F = 1, D = 1 Intervention provided by dedicated study staff: Efficacy study
Outcomes	Biochemically validated and self-reported quitting soon after the routine 36 week antenatal visit (late pregnancy*), reduction (mean cotinine*, self-reported*, and biochemically validated, which was at least half baseline measurement*), and increased smoking, mean birthweight*, preterm delivery*, very low birthweight*, low birthweight*, neonatal death*, stillbirths*, and admission to NICU* Data collected on other adverse events including antenatal admissions, miscarriage, termination of pregnancy, and assisted delivery Discussion of participant and provider views of intervention and thorough process evaluation showed good implementation
Notes	Sample size calculated by recruitment to achieve sufficient power not able to be achieved
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Stratified central randomisation.
Allocation concealment (selection bias)	Low risk	Group allocation provided by central administrator.
Incomplete outcome data (attrition bias) All outcomes	Low risk	29/762 (4%) women lost to follow-up: fetal loss = 6 (C = 2, I = 4) were excluded from this analysis; no late interview or cotinine = 10 (C = 5, I = 5), Not traceable 12 (C = 7, I = 5). Some missing data for cotinine validation All randomised participants (except fetal losses) included in smoking outcomes, and those with missing data counted as continuing smokers
Selective reporting (reporting bias)	Low risk	Detailed outcomes reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Serum cotinine (cut-off <13.7 ng/mL) or salivary cotinine (cut-off < 14.2 ng/mL) used to validate self-reported abstinence
Blinding of participants and personnel (performance bias) All outcomes	High risk	Midwife intervention, with caregivers not blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	‘A second administrator, blind to the random allocation, established a primary outcome’
Incomplete implementation	High risk	26% of women did not have any home visits.
Equal baseline characteristics in study arms	Low risk	No apparent major difference noted.
Contamination of control group	Low risk	Research midwives provided the intervention.