Does the risk of IUD expulsion warrant string checks?
The risk of IUD expulsion is estimated to be 1% at 1 month and 4% at 1 year, with a contraceptive failure rate of 0.4% at 1 year. The risk of expulsion does not differ by age group, including adolescents, or parity, but it is higher with use of the copper IUD (2% at 1 month, 6% at 1 year) and with prior expulsion (14%, limited by small numbers).1 Furthermore, risk of expulsion is higher with postplacental placement and second trimester abortion.14,15 Despite this risk, the contraceptive failure rate of all types of IUDs remains consistently lower than all other reversible methods besides the contraceptive implant.16
Furthermore, while IUD expulsion is rare, unnoticed expulsion is even more rare. In one study with more than 58,000 person-years of use, 132 pregnancies were noted, and 7 of these occurred in the setting of an unnoticed expulsion.13 Notably, a higher risk threshold is held for other medications. For example, statins are associated with a 3% risk of irreversible hepatic injury, yet serial liver function tests are not performed in patients without baseline liver dysfunction.17 A less than 0.1% risk of a non–life-threatening complication—unnoticed expulsion—does not warrant routine follow-up. Instead, the patient gauges the tolerability of that risk in making a follow-up plan, particularly given the varied individual preferences in patients’ management of the associated outcome of unintended pregnancy.
Are women interested in and able to perform their own string checks?
Recommendations to perform IUD string self-checks should consider whether women are willing and able to do so. In a study of 126 IUD users, 59% of women had attempted to check their IUD strings at home, and one-third were unable to do so successfully; all participants had visible strings on subsequent speculum exam.18 The women also were given the opportunity to perform a string self-check at the study visit. Overall, only 46% of participants found the exercise acceptable and were able to palpate the IUD strings.18 The authors aptly stated, “A universal recommendation for practice that is meant to identify a rare complication has no clinical utility if at least half of the women are unable to follow it.”
In which scenarios might a string check have clear utility?
The most important reason for follow-up after IUD placement or for patients to perform string self-checks is patient preference. At least anecdotally, some patients take comfort, particularly in the absence of menses, in palpating IUD strings regularly; these individuals should know that there is no necessity for but also no harm in this practice. In addition, patients may desire a string check or follow-up visit to discuss their new contraceptive’s goodness-of-fit.
While limited data show that routinely scheduling such visits does not improve contraceptive continuation, it is difficult to extrapolate these data to the select individuals who independently desire follow-up. (In addition, contraceptive continuance is hardly a metric of success, as clinicians and patients can agree that discontinuation in the setting of patient dissatisfaction is always appropriate.)
Clinicians should share with patients differing risks of IUD expulsion, and this may prompt more nuanced decisions about string checks and/or follow-up. Patients with postplacental or postabortion (second trimester) IUD placement or placement following prior expulsion may opt to perform string checks given the relatively higher risk of expulsion despite the maintained, absolutely low risk that such an event is unnoticed.
If a patient does present for a string check and strings are not visualized on exam, reasonable attempts should be made to identify the strings at that time. A cytobrush can be used to liberate and identify strings within the cervical canal. If the clinician cannot identify the strings or the patient is unable to tolerate such attempts, ultrasonography should be performed to localize the IUD. The ultrasound scan can be done in the office, if available, which is more cost-effective for women than a referral to radiology. If ultrasonography does not identify an intrauterine IUD, an x-ray is the next step to determine if the IUD has expulsed or perforated.
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