Castaño 2012.

Methods	Single site, parallel group, RCT Location: Brooklyn, NY, USA Time frame: enrolment from March 2008 to July 2009 Sample size calculation (and outcome of focus): detect 10% change in OC continuation between groups, assuming 40% continuation at 6 months in routine‐care group; N = 480 needed in each group
Participants	General with N: 962 women younger than 25 years Source: family planning health centre Inclusion criteria: sexually active; owned a cell phone with text messaging functionality; no medical contraindications to oral contraceptive use.
Interventions	Intervention: Routine care plus daily text messages for 180 days, i.e. reminders to take OC daily; education messages < 160 characters addressing 6 domains of OC knowledge (risks, benefits, side effects, use, effectiveness, and mechanisms of action). Comparison: Routine care, including contraceptive counseling and handout. Follow‐up: 6 months by telephone
Outcomes	OC continuation (participant had taken pill during the last 7 days), missed pills, interruptions in OC use > 7 days, use of OC at last sexual intercourse. Follow‐up: 6 months by telephone
Notes	Intention‐to‐treat analysis used Trial registration: ClinicalTrials.gov NCT 00677703 Funding: Trial was supported by grants from Affinity Health Plan Making a World of Difference Grant Program, William and Flora Hewlett Foundation. Declarations of interest: Two authors were advisory board members of pharmaceutical companies. The remaining authors did not report any potential conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table used with blocks of four
Allocation concealment (selection bias)	Low risk	Opaque, sequentially‐numbered, sealed envelopes. Investigators masked to allocation while randomizing
Blinding of participants and personnel (performance bias) All outcomes	High risk	None used
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information
Incomplete outcome data (attrition bias) All outcomes	High risk	Losses to follow‐up: 28% for treatment and 30% for control
Selective reporting (reporting bias)	Low risk	All outcomes prespecified in the protocol registered with ClinicalTrials.gov were reported on (in two publications)
Other bias	Unclear risk	Did not report objective outcome measures