Methods	Randomised controlled trial of intensive late pregnancy intervention to support ‘resistant’ smokers to stop smoking in pregnancy Study conducted in 3 large multispecialty clinics in Houstan and Dallas metropolitan areas, Texas (USA). Enrolment over a 17-month period, dates not specified
Participants	Inclusion criteria: Women were screened for eligibility into 2 concurrent studies: Pregnant women who smoked more than 5 cigarettes per week prior to pregnancy, fluent in English, over 18 years, less than 20 weeks’ gestation at first prenatal visit. Women who continue to smoke at 28 weeks’ gestation, after having counselling and 8 self-help booklets earlier in pregnancy care, and had telephone access, were eligible for this study Exclusion criteria: Women who had quit smoking at 28 weeks (continuous abstinence for 28 days),were enrolled in a large trial to prevent postpartum relapse (Project PANDA) Recruitment: 6956 (99%) women completed intake screening. 1255 current and recent smokers received brief intervention in early pregnancy as described by Ershoff 1989. 522/1255 (42%) had transferred care, had fetal demise or abortion, were over 34 weeks’ gestation, or could not be reached. All 269/733 (37%)who reported continuing to smoke at 28 weeks and were randomised to this study, as data collection and implementation were adopted as routine procedures, and required no formal written consent (C = 135, I = 134) Baseline characteristics: > 61 cigarettes/week before pregnancy: I = 57.9%, C = 43%; Partner smoking: C = 62.5%, I = 69.6% Mean age: C = 28.1, I = 28.6; Married: C = 71.1%, I = 65.7%, White: C = 76.3%, I = 81.3%. < high school: C = 11%, I = 9% Progress+ coding: None.
Interventions	Control: All women smoking at intake (< 20 weeks), were provided with MI counselling (3-5 mins) and a series of 8 motivational self-help books (first given in person and 7 mailed weekly thereafter), based on “stage of change” program as described by Ershoff 1989. Intervention: The high intensity intervention group (and their partners) then received: (i) a 20-30 min MI telephone counselling call (conducted by trained counsellors and nurse health educators), (ii) a personalised, stages of change based feedback letter, (iii) a final MI-based telephone call conducted 4-5 days after the feedback letter was sent The MI counselling calls were adapted from the Motivational Enhancement Therapy developed for Project MATCH (Miller 1992). Main intervention strategy: Counselling (multiple intervention) compared to less intensive intervention Intensity: Frequency: (C = 6, I = 6), Duration: (C = 1, I = 3). Intervention provided by dedicated project staff: efficacy study
Outcomes	Biochemically validated smoking cessation at 34 weeks’ gestation (late pregnancy*) Self-reported smoking cessation at 6 weeks, 3 months* and 6 months* postpartum Movement in “stages of change”. Breastfeeding rates and general health behaviours obtained but not reported Discussion of provider views.
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random number list.
Allocation concealment (selection bias)	Unclear risk	No details provided.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	35% attrition for cotinine testing: 175/269 provided cotinine subsample (C = 82, I = 84). 39% attrition for 6 weeks postpartum follow-up All women lost to follow-up for cotinine validated smoking status at 36/40 were included in this review as continuing smokers. Analysis includes all randomised women
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	Urinary cotinine analysis (cut-off 80 ng/mL) for a subset of the sample at 34 weeks’ gestation, but women without cotinine validation were included as continuing smokers. Postpartum outcomes self-reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel likely to have been aware of group allocation, though no formal consent requested
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Described as “single blind” (cotinine analysis performed blind)
Incomplete implementation	High risk	Only 55% of the experimental group received the full intervention (32% were never able to be reached). Implementation analysis suggested an effect in women who received full implementation: 43% vs 34% control group
Equal baseline characteristics in study arms	High risk	Group differences were found on number of cigarettes smoked per week at baseline, but no differences in demographic variables
Contamination of control group	Low risk	Specific counsellors delivered the intervention.