Background Immediate placement of an intrauterine device after vaginal delivery is safe and convenient, but longitudinal data describing clinical outcomes have been limited. Objective We sought to determine the proportion of TCu380A (copper) intrauterine devices expelled, partially expelled, malpositioned, and retained, as well as contraceptive use by 6 months postpartum, and determine risk factors for expulsion and partial expulsion. Study Design In this prospective, observational study, women who received a postplacental TCu380A intrauterine device at vaginal delivery were enrolled postpartum. Participants returned for clinical follow-up at 6 weeks, and for a research visit with a pelvic exam and ultrasound at 6 months. We recorded intrauterine device outcomes and 6-month contraceptive use. Partial expulsion was defined as an intrauterine device protruding from the external cervical os, or a transvaginal ultrasound showing the distal end of the intrauterine device below the internal os of the cervix. Multinomial logistic regression models identified risk factors associated with expulsion and partial expulsion by 6 months. The area under the receiver operating characteristics curve was used to assess the ability of a string check to predict the correct placement of a postplacental intrauterine device. The primary outcome was the proportion of intrauterine devices expelled at 6 months. Results We enrolled 200 women. Of 162 participants with follow-up data at 6 months, 13 (8.0%; 95% confidence interval, 4.7–13.4%) experienced complete expulsion and 26 (16.0%; 95% confidence interval, 11.1–22.6%) partial expulsion. Of 25 malpositioned intrauterine devices (15.4%; 95% confidence interval, 10.2–21.9%), 14 were not at the fundus (8.6%; 95% confidence interval, 5.2–14.1%) and 11 were rotated within the uterus (6.8%; 95% confidence interval, 3.8–11.9%). Multinomial logistic regression modeling indicated that higher parity (odds ratio, 2.05; 95% confidence interval, 1.21–3.50; P = .008) was associated with expulsion. Provider specialty (obstetrics vs family medicine; odds ratio, 5.31; 95% confidence interval, 1.20–23.59; P = .03) and gestational weight gain (normal vs excess; odds ratio, 9.12; 95% confidence interval, 1.90–43.82; P = .004) were associated with partial expulsion. Long-acting reversible contraceptive method use at 6 months was 80.9% (95% confidence interval, 74.0–86.6%). At 6 weeks postpartum, 35 of 149 (23.5%; 95% confidence interval, 16.9–31.1%) participants had no intrauterine device strings visible. Sensitivity of a string check to detect an incorrectly positioned intrauterine device was 36.2%, and specificity of the string check to predict a correctly positioned intrauterine device was 84.5%. This corresponds to an area under the receiver operating characteristics curve of 0.5. Conclusion This prospective assessment of postplacental TCu380A intrauterine device placement, with ultrasound to confirm device position, finds a complete intrauterine device expulsion proportion of 8.0% at 6 months. The association of increasing parity with expulsion is consistent with prior research. The clinical significance of covariates associated with partial expulsion (provider specialty and gestational weight gain) is unclear. Due to the observational study design, any associations cannot imply causality. The proportion of partially expelled and malpositioned intrauterine devices was high, and the area under the receiver operating characteristics curve of 0.5 indicates that a string check is a poor test for assessing device position. Women considering a postplacental intrauterine device should be counseled about the risk of position abnormalities, as well as the possibility of nonvisible strings, which may complicate clinical follow-up. The clinical significance of intrauterine device position abnormalities is unknown; future research should evaluate the influence of malposition and partial expulsion on contraceptive effectiveness and side effects.