In this nationwide cohort study comparing three doses of hormonal IUDs and copper IUDs, the highest dose (levonorgestrel 52 mg) was associated with the lowest risk of ectopic pregnancy within 1 year compared with copper IUDs, whereas the 13.5-mg hormonal IUD was associated with the highest risk. (Funded by the French National Fund for Health Insurance and the French National Agency for Medicines and Health Products Safety.).
Roland et al. (Tue,) studied this question.