title: Mechanisms of action of intrauterine devices: update and estimation of postfertilization effects.
abstract: There are many potential mechanisms of action for the intrauterine device (IUD), which vary by type of IUD (inert, copper, or hormonal). This paper reviews the evidence for each potential mechanism of action. On the basis of available data for fertilization rates and clinical pregnancy rates, the relative contribution of mechanisms acting before or after fertilization were quantitatively estimated. These estimates indicate that, although prefertilization effects are more prominent for the copper IUD, both prefertilization and postfertilization mechanisms of action contribute significantly to the effectiveness of all types of intrauterine devices.
authors.affiliation: Department of Family and Preventive Medicine, University of Utah Health Research Center, Salt Lake City 84108, USA. jstanford@dfpm.utah.edu
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Stanford
authors.forename: Rafael T
authors.initials: RT
authors.lastname: Mikolajczyk
mesh_terms: D002582:Cervix Mucus; D004717:Endometrium / Q000502:physiology; D005187:Fallopian Tubes / Q000166:cytology; D005260:Female; D005306:Fertilization; D006801:Humans; D007434:Intrauterine Devices; D007435:Intrauterine Devices, Copper; D007436:Intrauterine Devices, Medicated; D016912:Levonorgestrel; D016239:MEDLINE; D009865:Oocytes; D011247:Pregnancy; D011271:Pregnancy, Ectopic; D013083:Sperm Transport
chemical_list: D016912:Levonorgestrel