Svikis 2007.

Methods	RCT.
Participants	91 pregnant drug‐dependent women enrolled in comprehensive drug use treatment programme ‐ 18 years of age or older who met the DSM‐III‐R criteria for opiate, or cocaine dependence, or both.  Exclusion: Received methadone pharmacotherapy, delivered prematurely or aborted during study period, were administratively discharged from study, had extended or reduced residential stays, had acute psychiatric distress that prohibited study participation. Mostly in early 30s, 74% single/never married, 84% African American, and 95% unemployed, mean education of 11.2 years (SD = 1.9).  79.0% cocaine dependence, 37.1% opiate dependence, 17.7% alcohol dependence, and 17.7% cannabis dependence.
Interventions	For all participants, treatment included 7 days of residential care followed by 30 days intensive outpatient care.  Escalating voucher condition, also included an escalating voucher schedule for 14 days (starting at the first day of residential care). Participants had to attend a full day of counselling (4 hours) to earn a voucher. Initial incentive values were USD5 for Day 1 and increased USD5 per day for each consecutive day of treatment attendance up to USD70 for Day 14. Women could earn a maximum of USD525 for attending all 14 days of treatment. Participants were given one excused treatment day (n = 50). Control: Routine care – 7 days residential followed by 30 days outpatient care (n = 41).
Outcomes	Rate of premature residential treatment dropout against medical advice (AMA).  Length of stay in treatment.  Mean days prior to AMA.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Those providing informed consent were randomly assigned to either standard care or an escalating voucher schedule.." No specific description of randomization process used.
Allocation concealment (selection bias)	Unclear risk	No mention of allocation concealment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	As attrition is a primary outcome, incomplete data does not seem to be an issue.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessors not mentioned.