Menstrual cup use and intrauterine device expulsion in a copper intrauterine device randomized trial

Objective: To evaluate menstrual cup use and intrauterine device (IUD) expulsion. Study design: We performed a secondary analysis of a 3-year contraceptive efficacy trial comparing two copper 380 mm(2) IUDs. Investigators randomized participants approximately 1:4 to the TCu380A or NTCu380-Mini IUD. Approximately 12 months after enrollment began, we advised participants against menstrual cup use due to observed IUD expulsions in cup users. We evaluated IUD expulsion (including spontaneous partial and complete expulsion and accidental self-removal) at 12 and 36 months. We used multivariable logistic regression to evaluate IUD expulsion by age, baseline menstrual volume, body mass index, IUD type, menstrual cup use, parity, and uterine length. Results: This analysis included 1046 participants (203 TCu380A and 843 NTCu380-Mini), with 879 (84.0%) nulliparas. Through 12 and 36 months, expulsion occurred in 74 (7.1%, 95% CI 5.5-8.6%) and 133 (12.7%, 95% CI 10.7-14.7%) participants, respectively. Overall, 250 (23.9%) reported menstrual cup use. More menstrual cup users than non-users experienced expulsion through 12 months (32/ 203 [15.8%] vs. 42/843 [5.0%]) and 36 months (58/250 [23.2%] vs. 75/796 [9.4%]). Through 36 months, NTCu380-Mini menstrual cup users had higher expulsion odds, while TCu380A cup users did not. Menstrual cup users more frequently experienced accidental self-removal than non-users in participants using the TCu380A (3/53 [5.7%] vs. 0/150 [0.0%]) and the NTCu380-Mini (20/197 [10.2%] vs. 7/ 646 [1.1%]). In multivariable regression, we found increased odds of expulsion through 36 months in participants using menstrual cups with the NTCu380-Mini (aOR 3.13, 95% CI 1.16-8.46) and < 25 years (aOR 1.59, 95% CI 1.07-2.34). Conclusions: We found higher odds of IUD expulsion with menstrual cup and concurrent NTCu380-Mini IUD use over 36 months of use, but not with concurrent TCu380A IUD use. Menstrual cup users experienced higher likelihood of accidental self-removal regardless of IUD type. Implications: Menstrual cup and NTCu380-Mini use may increase IUD expulsion risk and may increase accidental self-removal risk with TCu380A and NTCu380-Mini use. Clinicians should advise patients of these risks and consider warning patients using an IUD shaped like the NTCu380-Mini (Nova-T frames) of expulsion risk with menstrual cup use.