Methods	Cluster-randomised controlled trial of a brief midwife-delivered intervention to support women to stop smoking in pregnancy Study conducted in nine hospital and community trusts in the UK. Years of data collection not reported
Participants	290 midwives randomised to provide intervention or control care Inclusion criteria: Pregnant women currently smoking or stopped within the last 3 months Exclusion criteria: Not further specified. Recruitment: Women were recruited at first visit (approximately 12 weeks’ gestation). Estimated 8700 eligible women. Only 178/290 (61%) midwives (C = 86, I = 92) recruited any women. Financial incentives were paid to boost recruitment. 1287 women provided informed consent Baseline characteristics: Current smokers (C = 440, I = 441); Spontaneous quitters (C = 135, I = 114). 189 current smokers were assessed as ‘not motivated to stop’ therefore received no intervention. Mean cigs/day: Smokers (C = 9.7, I = 10.1), Ex-smokers (C = 10.9, I = 12.6) > 70%married, 26%-27% smokers and 10%-15% ex-smokers had no educational qualifications Progress+ coding: None.
Interventions	Control: Midwives received 1 hour of training to discuss the study and were asked to provide usual care and any usual pamphlets Intervention: Midwives received 2 hours training which included using the CO monitor and providing ‘stage of change’ based advice, CO assessments. Intervention group also received written advice and motivational materials for current and recent smokers, including designating a ‘quit date’, a ‘quiz’ and the offer of ‘buddying’ to another pregnant smoker for support Main intervention strategy: Counselling (tailored) compared to usual care. Intensity: Frequency (C = 0, I = 5), Duration (C = 0, I = 2). Usual care intensity: F = 1, D = 1 Intervention provided by routine midwives: Effectiveness study
Outcomes	Biochemically validated point prevalence abstinence at birth (late pregnancy*), relapse prevention*, and self-reported continuous abstinence at 6 (6-11) months postpartum among baseline smokers* and spontaneous quitters. Birthweight for smokers and ex-smokers reported, but not by intervention group so not included in this review Participants and midwives views of interventions reviewed.
Notes	Clustering effect not reported, so sensitivity analysis conducted using 4 ICCs and outcome figures adjusted using conservative intracluster correlation of 0.1. See Table 2 for adjustment calculations for cluster trials. Discussion of barriers includes 65% of midwives reporting the intervention could not be undertaken in the time they had available. Sample size justification
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Cluster-randomisation of midwives adequate. Consecutive names on a list of midwives
Allocation concealment (selection bias)	Unclear risk	Midwives randomised.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	167/1287 (12.9%) (C = 83, I = 84) excluded from analysis due to moving away, being untraceable or deemed unsuitable for follow-up (e.g. miscarriage). 1120 in sample. 51/1287 non-responders were included as continuing smokers
Selective reporting (reporting bias)	Unclear risk	Unclear if all outcomes reported.
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	Low risk	Biochemical validation by expired CO < 10 ppm.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Midwives aware of allocation group. Educational intervention. Blinding women not feasible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessment not reported. Not blinded if performed by midwives
Incomplete implementation	High risk	Process evaluation showed poor implementation in some areas.
Equal baseline characteristics in study arms	High risk	Control group slightly more interested in quitting smoking and less nicotine dependent
Contamination of control group	Low risk	Cluster trial design to minimise risk of contamination.