BACKGROUND: We describe the rationale and protocol for a randomized noninferiority controlled trial (RCT) to determine if the Flexi-T380(+) copper intrauterine contraceptive device (IUD) is comparable in terms of effectiveness and expulsion rates to the most common Canadian IUD currently in use, NovaT-200, when placed immediately after a first-trimester abortion. METHODS/DESIGN: Consenting women choosing to use an IUD after an abortion for a pregnancy of less than 12 weeks of gestation will be randomized to device-type groups to receive immediate post-abortion placement of either a Flexi-T380(+) IUD, a device for which no current evidence on expulsion or effectiveness rates is available, or the Nova-T200 IUD, the only other brand of copper IUD available in Canada at the time of study initiation. The primary outcome measure is IUD expulsion rate at 1 year. Secondary outcomes include: pregnancy rate, method continuation rate, complication rates (infection, perforation), and satisfaction with contraceptive method. A non-intervention group of consenting women choosing a range of other post-abortion contraception methods, including no contraception, will be included for comparison of secondary outcomes. Web-based contraception satisfaction questionnaires, clinical records, and government-linked health administrative databases will be used to assess primary and secondary outcomes. DISCUSSION: The RCT design, combined with access to clinical records at all provincial abortion clinics, and to information in provincial single-payer linked administrative health databases, birth registry, and hospital records, offers a unique opportunity to determine if a novel IUD has a comparable expulsion rate to that of the current standard IUD in Canada, in addition to the first opportunity to determine pregnancy rate and method satisfaction at 1 year post-abortion for women choosing a range of post-abortion contraceptive options. We highlight considerations of design, implementation, and evaluation of the first trial to provide rigorous evidence for the effectiveness of current Canadian IUDs when inserted after first-trimester abortion. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT01174225.