Editing Copper IUD (section)

=== Contraceptive failure ===
[[File:Ultrasonography of IUD with copper.jpg|thumb|[[Transvaginal ultrasonography]] visualizing an IUD with copper in the optimal location within the uterus.]]

The absolute risk of [[ectopic pregnancy]] with IUD use is lower than with no contraception due to the dramatically decreased rate of pregnancy overall. However, when pregnancy does occur with a copper IUD in place, a higher percentage of those pregnancies are ectopic, from 3% to 6%, a two to sixfold increase. This corresponds to an absolute rate of ectopic pregnancy in copper IUD users of 0.2–0.4 per 1000 person-years, compared to 3 per 1000 person-years in the population using no contraception.<ref name=":4" /><ref name=":2" /><ref name="Good2010" />

If a pregnancy continues with the IUD in place, there is an increased risk of complications including preterm delivery, [[chorioamnionitis]], and spontaneous abortion. If the IUD is removed, these risks are lower, especially the risks of bleeding and miscarriage; the rate of miscarriage approaches that of the general population depending on study population.<ref name=":4">{{cite journal | vauthors = Molino GO, Santos AC, Dias MM, Pereira AG, Pimenta ND, Silva PH | title = Retained versus removed copper intrauterine device during pregnancy: An updated systematic review and meta-analysis | journal = Acta Obstetricia et Gynecologica Scandinavica | date = January 2025 | pmid = 39868878 | doi = 10.1111/aogs.15061 | doi-access = free | pmc = 11981102 }}</ref><ref name="Good2010" /><ref name=":2" />

Overall failure rates with the copper IUD are low, and are mainly dependent on the surface area of copper in the device. After 12 years of continuous use, the TCu{{Nbsp}}380A device has a cumulative pregnancy rate of 1.7%.<ref name="Good2010" /> The TCu 380A is more effective than the MLCu375, MLCu350, TCu220, and TCu200. The TCu 380S is more effective than the TCu 380A.<ref>{{cite journal | vauthors = Kulier R, O'Brien PA, Helmerhorst FM, Usher-Patel M, D'Arcangues C | title = Copper containing, framed intra-uterine devices for contraception | journal = The Cochrane Database of Systematic Reviews | issue = 4 | pages = CD005347 | date = October 2007 | pmid = 17943851 | doi = 10.1002/14651858.CD005347.pub3 | collaboration = Cochrane Fertility Regulation Group }}</ref> The frameless device has similar failure rates to conventional devices.<ref name=":9" />