The 13.5-mg, 19.5-mg, and 52-mg Levonorgestrel-Releasing Intrauterine Systems and Risk of Ectopic Pregnancy

To assess the Pearl Index for risk of ectopic pregnancy in women using levonorgestrel-releasing intrauterine systems (LNG-IUS) with hormonal reservoirs of 13.5 mg, 19.5 mg, or 52 mg.

This was a retrospective cohort study. Women diagnosed with an ectopic pregnancy in Stockholm County, Sweden, between January 1, 2014, and December 31, 2019, were identified through the electronic medical record system. The final analysis included 2,252 cases of ectopic pregnancy. Information on age, reproductive and medical history, as well as current use of contraception was retrieved. The time of intrauterine device (IUD) insertion before ectopic pregnancy and the numbers of sold LNG-IUS during the study period were used to calculate the incidence rate for ectopic pregnancy during use per 100 woman-years (Pearl Index).

Among women with an ectopic pregnancy diagnosis, 105 presented with a known type of hormonal IUD in situ, of whom 94 were included in the calculations of the Pearl Index. The estimated Pearl Index for ectopic pregnancy was 0.136 (95% CI 0.106-0.176) for the LNG-IUS 13.5-mg, 0.037 (95% CI 0.021-0.067) for the LNG-IUS 19.5-mg, and 0.009 (95% CI 0.006-0.014) for the LNG-IUS 52-mg. With the 52-mg LNG-IUS as referent, the relative risk (RR) for ectopic pregnancy was higher during the first year for LNG 13.5-mg (RR 20.59, 95% CI 12.04-35.21), and for both 13.5-mg (RR 14.49, 95% CI 9.01-23.3) and 19.5-mg (RR 4.44, 95% CI 1.64-12.00) during the total study period.

The absolute risk of ectopic pregnancy during the use of LNG-IUS at any doses was low. The results show that the lower the dose of the IUD, the higher the risk of an ectopic pregnancy. Higher-dose LNG-IUS should be considered when providing contraceptive counseling to a woman with known risk factors for ectopic pregnancy who are considering a hormonal IUD.