Intrauterine contraception compasses both copper (Cu-IUD) and hormone (i.e., progestin levonorgestrel [LNG]) releasing IUDs (LNG-IUD). There are multiple types and manufacturers of Cu-IUDs and fewer LNG-IUDs. The approved duration of use varies from 3 to 10 years for different IUDs. The mechanisms of action of the two types of IUD differ—the contraceptive efficacy of Cu-IUD is mediated mainly via the toxic effects of Cu on germ cells (mainly sperm), whereas the LNG-IUD acts via making the cervical mucus impermeable to sperm and suppressing the endometrium. Both types of IUDs are very effective—commonly cited Pearl indexes (the number of contraceptive failures (i.e., pregnancies) during the first year of use in 100 fertile-aged women using the method of Cu-IUD is 0.6 and 0.2 for the LNG-IUD). In addition, the continuation rate of both types of IUDs is high with approximately 80% of continuing their use at 1 year. IUD use is associated with very few health risks. Adverse events specific to IUD contraception include expulsion and uterine perforation. Unnoticed expulsion is not a rare adverse event and per se not dangerous, but it exposes the user to a risk of unplanned pregnancy. The overall rate of expulsion is approximately 5% during 5 years of use, but it varies according to timing of insertion (immediate postpartum/abortal vs. interval insertion). Uterine perforation by IUD is a rare event occurring in approximately 1/1000–2000 insertions. IUD perforation is rarely dangerous, and approximately one-third of all perforations are asymptomatic and diagnosed incidentally. The risk is increased several folds in insertions occurring within 6 months postpartum in lactating women. Conversely, more than 99% of also these IUD insertions do not perforate. The association of ectopic pregnancy with IUD contraception is a cause of common misconceptions. IUD use decreases the incidence of ectopic pregnancy in comparison to women not using contraception. However, as IUDs are more effective in preventing intrauterine pregnancy, the percentage of ectopic pregnancies of all pregnancies started during IUD contraception is increased. The profile of potential side effects of IUD varies according to device. The use of Cu-IUD may result in increased menstrual bleeding, whereas menstrual bleeding is typically greatly diminished during LNG-IUD use. Being a hormonal method, the use of LNG-IUD is associated with slightly increased risk of breast cancer, yet the risks of uterine and ovarian cancer are decreased during LNG-IUD use. Also, the risk of cervical cancer is decreased during IUD use. The very high contraceptive efficacy of IUDs was highlighted globally via publication of the CHOICE study in 2012. Importantly, the study highlighted that IUDs are equally effective in all women, also in highly fertile adolescent women. Consequently, several international organizations on contraception currently recommend IUDs as first-line contraceptives to all women irrespective of their age or parity.

Intrauterine Devices: Efficacy and Risks: Insights from the Real-World Evidence

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发表日期：

2026年

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Oskari Heikinheimo

摘要

Intrauterine contraception compasses both copper (Cu-IUD) and hormone (i.e., progestin levonorgestrel [LNG]) releasing IUDs (LNG-IUD). There are multiple types and manufacturers of Cu-IUDs and fewer LNG-IUDs. The approved duration of use varies from 3 to 10 years for different IUDs. The mechanisms of action of the two types of IUD differ—the contraceptive efficacy of Cu-IUD is mediated mainly via the toxic effects of Cu on germ cells (mainly sperm), whereas the LNG-IUD acts via making the cervical mucus impermeable to sperm and suppressing the endometrium. Both types of IUDs are very effective—commonly cited Pearl indexes (the number of contraceptive failures (i.e., pregnancies) during the first year of use in 100 fertile-aged women using the method of Cu-IUD is 0.6 and 0.2 for the LNG-IUD). In addition, the continuation rate of both types of IUDs is high with approximately 80% of continuing their use at 1 year. IUD use is associated with very few health risks. Adverse events specific to IUD contraception include expulsion and uterine perforation. Unnoticed expulsion is not a rare adverse event and per se not dangerous, but it exposes the user to a risk of unplanned pregnancy. The overall rate of expulsion is approximately 5% during 5 years of use, but it varies according to timing of insertion (immediate postpartum/abortal vs. interval insertion). Uterine perforation by IUD is a rare event occurring in approximately 1/1000–2000 insertions. IUD perforation is rarely dangerous, and approximately one-third of all perforations are asymptomatic and diagnosed incidentally. The risk is increased several folds in insertions occurring within 6 months postpartum in lactating women. Conversely, more than 99% of also these IUD insertions do not perforate. The association of ectopic pregnancy with IUD contraception is a cause of common misconceptions. IUD use decreases the incidence of ectopic pregnancy in comparison to women not using contraception. However, as IUDs are more effective in preventing intrauterine pregnancy, the percentage of ectopic pregnancies of all pregnancies started during IUD contraception is increased. The profile of potential side effects of IUD varies according to device. The use of Cu-IUD may result in increased menstrual bleeding, whereas menstrual bleeding is typically greatly diminished during LNG-IUD use. Being a hormonal method, the use of LNG-IUD is associated with slightly increased risk of breast cancer, yet the risks of uterine and ovarian cancer are decreased during LNG-IUD use. Also, the risk of cervical cancer is decreased during IUD use. The very high contraceptive efficacy of IUDs was highlighted globally via publication of the CHOICE study in 2012. Importantly, the study highlighted that IUDs are equally effective in all women, also in highly fertile adolescent women. Consequently, several international organizations on contraception currently recommend IUDs as first-line contraceptives to all women irrespective of their age or parity.