Abstract: Objective： To evaluate the risk factors of ectopic intrauterine device （IUD），so as to prevent the adverse events of ectopic IUD，and to conduct the safest use of IUDs. Methods： By analyzing the top six adverse events of IUDs which submitted to the database of National Population and Family Planning Commission （NPFPC） contraceptive adverse reaction monitoring center，we explored the incidences of IUDs adverse events，patient's characteristics such as age，parity and breastfeeding status，to analyze the risk factors of ectopic IUDs. Results： The top six IUDs were MCu IUD，TCu220C，medicated stainless steel ring-165 （containing copper），YuanGong IUD，stainless steel ring，copper uterine cavity-shaped intrauterine devices （UCD200）. Totally，there were 236 ectopic IUDs. 210 IUDs （88.98%） were partial embedded into the endometrial and muscular layer，6 IUDs （2.54%） were complete into the endometrial and muscular layer，20 IUDs （38.98%） were migrated outside the uterus. Abdominal pain was the main events detected in the clinical symptoms. The close-model IUDs got higher risk of translocation following the transfer time of IUDs （P<0.000 1）. Conclusionｓ： IUDs type and the time after transfer might be associated with the ectopic IUDs. Abdominal pain was trigger for detection of ectopic IUDs. Women with IUDs should have regular follow-up visits.

Key words: Intrauterine devices, Risk factors, Pain