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 mm² 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.

Background

The most widely used copper intrauterine device (IUD) in the world (the TCu380A), and the only product available in many countries, causes side effects and early removals for many users. These problems are exacerbated in nulliparous women, who have smaller uterine cavities compared to parous women. We compared first-year continuation rates and reasons/probabilities for early removal of the TCu380A versus a smaller Belgian copper IUD among nulliparous users.

Methods

This 12-month interim report is derived from a pre-planned interim analysis of a sub population and focused on key secondary comparative endpoints. In this participant-blinded trial at 16 centres in the USA, we randomised participants aged 17-40 in a 4:1 ratio to the NT380-Mini or the TCu380A. In the first year, participants had follow-up visits at 6-weeks and 3, 6, and 12-months, and a phone contact at 9 months; we documented continued use, expulsions, and reasons for removal. Among participants with successful IUD placement, we compared probabilities of IUD continuation and specific reasons for discontinuation using log-rank tests. This trial is registered with ClinicalTrials.gov number NCT03124160 and is closed to recruitment.

Findings

Between June 1, 2017, and February 25, 2019, we assigned 927 nulliparous women to either the NT380-Mini (n = 744) or the TCu380A (n = 183); the analysis population was 732 (NT380-Mini) and 176 (TCu380A). Participants using the NT380-Mini, compared to the TCu380A, had higher 12-month continuation rates (78·7% [95% CI: 72·9-84·5%] vs. 70·2% [95% CI: 59·7-80·7], p = 0·014), lower rates of removal for bleeding and/or pain (8·1% vs. 16·2%, p = 0·003) and lower IUD expulsion rates (4·8% vs. 8·9%, p = 0·023), respectively.

Interpretation

The NT380-Mini offers important benefits for a nulliparous population compared to the TCu380A in the first twelve months, when pivotal experiences typically occur. Higher continuation rates with the NT380-Mini may avert disruptions in contraceptive use and help users avoid unintended pregnancy.

Funding

Bill & Melinda Gates Foundation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and Mona Lisa, N.V. (Belgium).