ImportanceThe early postpartum period, 2 to 4 weeks after birth, may be a convenient time for intrauterine device (IUD) placement; the placement could then coincide with early postpartum or well-baby visits.ObjectiveTo determine expulsion rates for IUDs placed early postpartum compared with those placed at the standard interval 6-week visit.Design, Setting, and ParticipantsIn this randomized noninferiority trial, people who had a vaginal or cesarean birth were randomly assigned to undergo early (14-28 days) or interval (42-56 days) postpartum IUD placement. Clinicians blinded to participant study group used transvaginal ultrasonography to confirm IUD presence and position at the 6-month postpartum follow-up. The study assessed 642 postpartum people from 4 US medical centers, enrolled a consecutive sample of 404 participants from March 2018 to July 2021, and followed up each participant for 6 months postpartum.InterventionsEarly postpartum IUD placement, at 2 to 4 weeks postpartum, vs standard interval placement 6 to 8 weeks postpartum.Main Outcomes and MeasuresThe primary outcome was complete IUD expulsion by 6 months postpartum; the prespecified noninferiority margin was 6%. Secondary outcomes were partial IUD expulsion, IUD removal, pelvic infection, patient satisfaction, uterine perforation, pregnancy, and IUD use at 6 months postpartum. IUD malposition was an exploratory outcome.ResultsAmong 404 enrolled participants, 203 participants were randomly assigned to undergo early IUD placement and 201 to undergo interval IUD placement (mean [SD] age, 29.9 [5.4] years; 46 [11.4%] were Black, 228 [56.4%] were White, and 175 [43.3%] were Hispanic). By 6 months postpartum, 53 participants (13%) never had an IUD placed and 57 (14%) were lost to follow-up. Among the 294 participants (73%) who received an IUD and completed 6-month follow-up, complete expulsion rates were 3 of 149 (2.0% [95% CI, 0.4%-5.8%]) in the early placement group and 0 of 145 (0% [95% CI, 0.0%-2.5%]) in the interval placement group (between-group difference, 2.0 [95% CI, −0.5 to 5.7] percentage points). Partial expulsion occurred in 14 (9.4% [95% CI, 5.2%-15.3%]) participants in the early placement group and 11 (7.6% [95% CI, 3.9%-13.2%]) participants in the interval placement group (between-group difference, 1.8 [95% CI, −4.8 to 8.6] percentage points). IUD use at 6 months was similar between the groups: 141 (69.5% [95% CI, 62.6%-75.7%]) participants in the early group vs 139 (67.2% [95% CI, 60.2%-73.6%]) in the interval group.Conclusions and RelevanceEarly IUD placement at 2 to 4 weeks postpartum compared with 6 to 8 weeks postpartum was noninferior for complete expulsion, but not partial expulsion. Understanding the risk of expulsion at these time points may help patients and clinicians make informed choices about the timing of IUD placement.Trial RegistrationClinicalTrials.gov Identifier: NCT03462758