Silverman 2001.

Methods	RCT. Groups similar in terms of demographic and baseline drug use.
Participants	40 pregnant, unemployed, women 18 to 50 years old on MMT, and with positive urine toxicology for opiates within 6 weeks prior to enrolment. Mean age 32; 83% African America; 65% HS or greater education; 7.5% married; 100% unemployed; 100% used cocaine; 75% used cocaine. Exclusion: at risk for suicide, psychiatric disorder.
Interventions	For all participants, substance abuse counselling and MMT provided. Details of counselling not given. No mention of MMT doses or schedule. Therapeutic workplace 3 hours/day for 6 months. Job skills training provided. Base‐pay voucher given out at the end of shift. Entrance to workplace contingent upon negative urine sample. Job skills focused on data entry. Vouchers used to promote abstinence and maintain workplace attendance (n = 20). "Routine" drug treatment services provided by the centre. Details not given (n = 20). Duration 24 weeks.
Outcomes	Retention in treatment defined as remaining in the study through 24 weeks and reported as N and %. Urine toxicology reported as % negative over total study period for each group, and reported as overall positive and drug‐specific positive. Attendance in Therapeutic Workplace was calculated and presented in a bar graph for each woman.
Notes	Transportation and childcare provided at no cost. We attempted to contact trial authors but received no answer.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A modified dynamic balanced randomization was used to randomize patients sequentially to the treatment conditions."
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was not described.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition details outlined, reasons for leaving also outlined. Different methods utilized to attempt to account for missing data.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No references to outcome assessor blinding made.