Sivin 1998.

Methods	Design: randomized controlled trial; focused on effectiveness of reformulated 2‐rod LNG implant versus 6‐rod implant Location: 7 centers including USA and Finland Time frame: enrollment 1990 to 1994 Sample size estimation and outcome of focus: assumed 50/100 acceptors would continue; pregnancy rate 2.0/100 at 3 years with SE 0.66/100; sample size could distinguish difference in pregnancy of 2/100 between 2 implant types
Participants	1200 healthy women, 18 to 40 years old, who sought implant contraception Inclusion criteria: no contraindication to implant use; willing to undergo study procedures Exclusion criteria: cancer; severe cardiovascular problem; hyperlipidemia; diabetes mellitus; mental illness; epilepsy; severe or frequent headaches; undiagnosed genital bleeding; hyperprolactinemia or bloody breast discharge; pelvic inflammatory disease since last pregnancy or ectopic pregnancy
Interventions	Levonorgestrel implants 1) Norplant: 6 capsules containing levonorgestrel 216 mg (total) 2) LNG rod (Jadelle): 2 rods containing levonorgestrel 150 mg (total); different elastomer in core than earlier implant Follow‐up: 1, 3, 6 months; then semi‐annually to 5 years
Outcomes	Mean weight change by implant group Weight change for 10th, 50th, and 90th percentiles of body weight (at admission) Follow‐up: 5 years Weighing method not specified
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization by "linear congruential method"; blocks of 50 per clinic
Allocation concealment (selection bias)	Low risk	Implants in sealed opaque envelopes numbered sequentially according to randomization lists
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not feasible due to apparent differences in interventions
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information; objective outcome measures
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up: year 3, 2.7% each group; year 5, 7.2% LNG rod and 10.2% Norplant Discontinuation: end of year 3, LNG rod 31.6% (190/600) and Norplant 31.2% (187/598); end of year 5, LNG rod 54.7% (328/600) and Norplant 60% (359/598) 2 sets of Norplant contaminated and not used (1198/2000 analyzed)