Peipert 2008.

Methods	Design: randomized controlled trial Location: Rhode Island (USA); recruitment Oct 1999 to Oct 2003 Sample size calculation (and outcome of focus): N=250 in each group to detect two‐fold increase in dual method use and 50% difference in unintended pregnancy.
Participants	General with N: 542 women Source: primary care and family planning clinics Inclusion criteria: 13 to 35 years old, sex with man in past 6 months, desire to avoid pregnancy for 24 months; if age 25 to 35 years, then high‐risk history (unplanned pregnancy, STIs, inconsistent contraception use, > 1 sex partner in past 6 months, drug or alcohol abuse). Exclusion criteria: currently using dual methods of contraception consistently and correctly.
Interventions	Study focus: STI and pregnancy prevention Theory or model: transtheoretical model Treatment: 3 sessions over 80 days; individually‐tailored, computer‐delivered; designed to move toward action and maintenance for dual‐method use and recycling through relapse. Comparison or control: 1 session, computer‐delivered, standard contraception and STI prevention information. Duration: return visits at 12 and 24 months.
Outcomes	Dual‐method use (hormonal + barrier; male condoms + female condoms; condoms + spermicide; intrauterine device + barrier), initiated or sustained (reported at 2 or more interviews); consistent condom use; unplanned pregnancy (tested); STIs.
Notes	Investigator communicated that the code book did not contain data on attitudes about dual‐method use as the report indicated; the manuscript must have contained an error. An investigator noted that they assessed self‐efficacy for condom use and non‐condom contraceptive use separately.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer program; stratified by site and contraceptive use
Allocation concealment (selection bias)	Unclear risk	Computer allocated women after collecting baseline information; separate from executor of assignment (phone interviewer and nurse doing exams)
Blinding of participants and personnel (performance bias) All outcomes	High risk	No mention; presume none since blinding is not usually feasible for educational interventions.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Follow‐up evaluators were 'masked' to allocation as far as possible
Incomplete outcome data (attrition bias) All outcomes	High risk	Losses to follow up: 26% by 24 months (groups had similar losses) 2011 paper: N=463; 15% had no follow‐up data Exclusions after randomization: no; intent‐to‐treat analysis
Selective reporting (reporting bias)	Low risk	Not apparent