Kirby 2010.

Methods	Design: RCT Location: San Francisco, CA (USA) Time frame: July 2005 to August 2007 Sample size calculation and outcome of focus: 80% power to detect 10‐percentage‐point difference between groups in the proportion of women who used hormonal contraception for 6 months or longer, needed 600 women; with expected follow‐up 75%, planned to enroll 800
Participants	General with N: 805 young women, 14 to 18 years old Source: reproductive health clinic for adolescents and young adults Inclusion criteria: not pregnant or trying to become pregnant; had sex in the last 3 months; no consistent hormonal contraception for 3 months and no IUD or contraceptive implant Exclusion criteria: no information
Interventions	Study focus: improve contraceptive use; reduce unintended pregnancy and STI Theory or model: motivational interviewing; Health Belief Model Intervention: intense phone follow‐up after initial visit; 9 calls planned (1 per month for 6 months then every 2 months for 6 months); addressed effective use of contraceptives and superiority of hormonal methods over condoms for preventing pregnancy Comparison: usual care (no phone follow‐up) Duration: 12 months
Outcomes	Primary: hormonal contraceptive use at last sex, condom use at last sex, self‐reported pregnancy; completed online at youth center or phone survey Secondary: no information Additional data from investigator (2010): pregnancy rates by group (self report and clinic charts); effect sizes and P values for outcomes without detail in report Follow‐up: 6, 12, 18 months after baseline
Notes	Analysis: multiple linear and logistic regression repeated measures; adjusted for differences between groups
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number generator; participants stratified by age
Allocation concealment (selection bias)	Unclear risk	No information
Blinding of participants and personnel (performance bias) All outcomes	High risk	Research team blind to group composition until after analysis of primary hypothesis. Presume no blinding of participants or providers; not feasible due to type of intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome assessor unaware of group assignment, except for final follow‐up, which included questions about intervention
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up: 6 months 22%, 12 months 26%, 18 months 25%; reportedly did not differ by group No N per group for assessments