Baker 2018.

Methods	2‐group randomised clinical trial. 2012 to 2016 Country: USA Setting: A perinatal support programme (First breath (FB)). Private and community health clinics providing perinatal healthcare services across Wisconsin as part of the FB programme
Participants	1014 pregnant women, aged 18+, smoking daily (at least 1 CPD each day for at least 1 week) at some time within the last 6 months, enrolled in Wisconsin Medicaid (BadgerCare Plus or Medicaid SSI). Intervention n = 505, control n = 509. Mean age 26, ethnicity: % white CG: 47.2% IG: 45.4%, black or African American CG: 36.9% IG: 39.8%, Asian CG: 0.8% IG: 0.2%, American Indian/Alaska Native CG: 2.0% IG: 1.0%, 'Other' CG: 2.8% IG: 1.0%, Refused/do not know/missing CG: 7.5% IG: 8.5%, Hispanic CG: 5.3% IG: 4.8%, Non‐Hispanic CG: 81.7% IG: 81.8%, Refused to answer/missing CG: 13.0% IG: 13.5% Education % Less than high school CG: 3.7% IG: 4.2%, Some high school CG: 20.6% IG: 20.6%, High school or GED CG: 34.2% IG: 34.3%, Some college or 2‐year degree CG: 25.55 IG: 22.0%, College degree CG: 3.0% IG: 5.4%, Refused to answer/missing CG: 13.0% IG: 13.7%. CPD: 1 to 10 CG: 39.3% IG: 38.4%; 11 to 20 CG: 39.1% IG: IG: 39.4%; 20+ CG: 17.5% IG: 19.4%; Refused to answer/missing CG: 4.1% IG: 2.8%
Interventions	Control Group: The study compensated all participants USD 40 for study registration/enrolment and USD 40/visit for attendance at post‐birth Visit 1 (1 to 3 weeks post‐birth) and post‐birth Visit 4 (at month 6). Participants attending visits 1 and 4 completed CO testing to biochemically verify self‐reports of abstinence from smoking; participants with CO test values of 7 ppm were considered to be abstinent. Thus, control condition participants could receive up to USD 120 Experimental Group(s): Incentive condition participants received a further USD 25/visit for any of the 6 pre‐birth visits they completed, USD 25/visit for attendance at post‐birth visits 2 and 3, USD 20/call for completion of 5 post‐birth calls, and USD 40/visit for biochemically‐confirmed abstinence at post‐birth visits 1 and 4. Thus, incentive condition participants could receive up to USD 500 for meeting all payment criteria Theoretical basis for intervention: not reported Duration of intervention: 6 months post‐birth Length of follow‐up: 6 months post‐birth
Outcomes	PPA at 6 months with cut‐off CO < 7 ppm. Number of post‐birth home visits and phone calls taken; biochemically‐confirmed abstinence at the post‐birth week 1 visit; and self‐reported smoking status at the 2‐ and 4‐month visits Engagement in treatment and cost effectiveness also cited on NCT record but not reported
Notes	New for 2019 update’ Previously listed as ongoing Funding: not reported Decarations of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	FB staff used randomisation tables prepared by the UW‐CTRI to randomise women upon consent. Separate computer determined randomisation tables were created based on race (white/non‐white) and county with proportional randomisation (1:1) into the incentive and control conditions
Allocation concealment (selection bias)	Unclear risk	Allocation not reported
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Results were CO‐verified
Incomplete outcome data (attrition bias) All outcomes	Low risk	For the primary outcome, 316 of 509 (37.9%) control condition participants had missing data; 145 of 505 (28.7%) incentive condition participants had missing data. Participants with missing data for the primary outcome were counted as smoking (ITT)
Other bias	Unclear risk	6‐month follow‐up stated for primary outcome, but Table 2 results reports "4‐6 months" follow‐up